PWA (Progressive Web App)是一种渐进式Web应用程序，它是基于Web技术构建的应用程序，可以像本地应用程序一样运行在各种设备和平台上，包括桌面、移动设备和平板电脑等。

PWA具有许多本地应用程序的功能，例如离线访问、推送通知、主屏幕快捷方式等，同时还具有网页应用程序的优势，例如可访问性、跨平台性等。PWA可以通过Web浏览器安装到设备中，无需通过应用商店进行下载和安装。

PWA使用一组现代Web技术，例如Service Workers、Web App Manifests、HTTPS等，以提供一个类似于本地应用程序的体验。使用PWA，用户可以在设备上安装应用程序，无需访问应用商店，而且在网络不可用时，应用程序仍然可以正常工作。

PWA是一种新兴的Web技术，它正在成为Web应用程序的未来，许多公司和组织正在将其应用于其Web应用程序，以提供更好的用户体验和更高的用户参与度。

在Android WebView中使用Service Worker涉及到几个关键步骤。首先，确保你的WebView设置允许Service Workers的使用。接下来，必须在你的Web内容中实现Service Worker，并确保它可以在WebView上注册。以下是步骤的概览：

### 1. 配置WebView
在你的Android应用中，你需要配置WebView以支持Service Worker。主要是需要启用JavaScript和Web存储APIs。

```java
WebView myWebView = (WebView) findViewById(R.id.webview);
WebSettings webSettings = myWebView.getSettings();

// 启用JavaScript
webSettings.setJavaScriptEnabled(true);

// 启用Dom存储功能，这对于Service Workers很重要
webSettings.setDomStorageEnabled(true);

// 如果你的应用需要支持跨域请求
// 从Android 5.0 (Lollipop) 开始，WebView默认不允许跨源请求
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    myWebView.getSettings().setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
}
```

### 2. 实现Service Worker
在你的Web应用中，你需要有一个Service Worker的JavaScript文件。例如，`service-worker.js` 包含了Service Worker的安装、激活和拦截请求的逻辑。

```javascript
// service-worker.js
self.addEventListener('install', event => {
    // 安装逻辑
});

self.addEventListener('activate', event => {
    // 激活逻辑
});

self.addEventListener('fetch', event => {
    // 请求拦截逻辑
});
```

### 3. 注册Service Worker
在你的Web页面的JavaScript中，你需要注册Service Worker脚本。

```javascript
if ('serviceWorker' in navigator) {
    navigator.serviceWorker.register('/service-worker.js')
    .then(function(registration) {
        // 注册成功
        console.log('Service Worker 注册成功: ', registration);
    })
    .catch(function(error) {
        // 注册失败
        console.log('Service Worker 注册失败: ', error);
    });
}
```

### 4. 处理兼容性和错误
不是所有的Android WebView版本都支持Service Worker。你需要确保你的用户在一个支持Service Worker的环境中。此外，在注册过程中，可能会遇到各种错误，需要妥善处理这些错误。

### 5. 测试
在实现Service Worker之后，你需要在Android设备上进行测试，以确保Service Worker的行为符合预期。

### 示例
以下是一个简化的例子，演示如何在Android App的WebView中使用Service Worker。

**MainActivity.java**
```java
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WebView myWebView = (WebView) findViewById(R.id.webview);
        WebSettings webSettings = myWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webSettings.setDomStorageEnabled(true);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            myWebView.getSettings().setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
        }

        myWebView.loadUrl("https://your-web-app.com");
    }
}
```

这只是一个基本的介绍，具体实现细节可能因您的应用需求和Android版本而异。记得在不同的设备和Android版本上进行全面的测试，以确保最佳的兼容性和性能。

How to use service workers in android WebView?

Service Worker本身并不能直接持久化数据，但是它可以通过使用浏览器提供的存储API来实现数据持久化。以下是在Service Worker中持久化数据的几种方法：

### 1. 使用 IndexedDB

IndexedDB 是一个运行在浏览器中的非关系型数据库，它允许你存储大量结构化数据。Service Worker 可以通过 IndexedDB来持久化数据。这个API设计用来存储大量数据，并且支持事务。

**例子:**

假设我们想要在Service Worker中缓存并持久化一些用户数据：

```javascript
self.addEventListener('install', (event) => {
  event.waitUntil(
    (async () => {
      const dbOpenRequest = indexedDB.open('myDatabase', 1);

      dbOpenRequest.onupgradeneeded = function(event) {
        let db = event.target.result;
        db.createObjectStore('userData', { keyPath: 'id' });
      };

      const db = await dbOpenRequest;
      const tx = db.transaction('userData', 'readwrite');
      const store = tx.objectStore('userData');
      store.put({ id: 1, name: 'John Doe', email: 'john@example.com' });
      await tx.complete;
    })()
  );
});
```

### 2. 使用 Cache API

Cache API 提供了一个持久化缓存请求和它们相应返回的能力，非常适合用于存储应用外壳（即应用的静态部分，比如HTML, CSS, JavaScript文件等）。

**例子:**

以下代码片段展示了如何使用Cache API 缓存和获取资源：

```javascript
self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open('my-cache').then((cache) => {
      return cache.addAll([
        '/index.html',
        '/styles.css',
        '/script.js',
        // 其他资源...
      ]);
    })
  );
});

self.addEventListener('fetch', (event) => {
  event.respondWith(
    caches.match(event.request).then((response) => {
      return response || fetch(event.request);
    })
  );
});
```

### 3. 使用 LocalStorage

虽然Service Worker 没有直接访问`localStorage`的权限，但是你可以通过Client API向页面发送消息，由页面再将数据持久化到`localStorage`。

**例子:**

这需要Service Worker和页面之间的通信。Service Worker发送消息给页面：

```javascript
self.clients.matchAll().then(clients => {
  clients.forEach(client => {
    client.postMessage({
      command: 'storeData',
      data: { key: 'value' }
    });
  });
});
```

然后，在页面中监听Service Worker发来的消息并使用 `localStorage`:

```javascript
navigator.serviceWorker.addEventListener('message', event => {
  if (event.data.command === 'storeData') {
    localStorage.setItem('myKey', event.data.data.key);
  }
});
```

### 4. 使用 Web SQL (不推荐)

Web SQL是一个已经不被推荐使用的Web API，因为它不是W3C标准，而且已经被大多数现代浏览器废弃。

综上所述，对于在Service Worker中持久化数据，通常建议使用IndexedDB或Cache API，它们都被现代浏览器广泛支持，并且专为工作线程和Service Worker设计，以支持大量数据，且能在没有网络连接的情况下有效工作。

How to persist data in a Service Worker

### 离线视频内容的支持是 Progressive Web Apps（PWA）中的一项重要功能，它可以提高用户的体验，尤其是在网络连接不稳定或没有网络的环境下。以下是通过PWA实现离线视频内容的步骤以及实际案例：

#### 步骤 1: 注册 Service Worker
首先，需要在你的PWA中注册一个 Service Worker。Service Worker 是一种运行于浏览器背后的脚本，能够处理网络请求，缓存文件，并使应用能够运行离线。

```javascript
if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/service-worker.js')
    .then(function(registration) {
      console.log('Service Worker 注册成功: ', registration);
    })
    .catch(function(error) {
      console.log('Service Worker 注册失败: ', error);
    });
}
```

#### 步骤 2: 缓存视频内容
在 Service Worker 中，你可以利用 Cache API 来缓存视频文件。通常在 Service Worker 的 install 事件中处理缓存逻辑。

```javascript
self.addEventListener('install', function(event) {
  event.waitUntil(
    caches.open('video-cache').then(function(cache) {
      return cache.addAll([
        // 列出所有需要缓存的视频文件
        '/videos/video1.mp4',
        '/videos/video2.mp4',
      ]);
    })
  );
});
```

#### 步骤 3: 拦截请求并响应离线内容
当用户尝试访问视频时，Service Worker 应该能够拦截这些请求，并从缓存中提供视频内容，即使在离线状态下也是如此。

```javascript
self.addEventListener('fetch', function(event) {
  event.respondWith(
    caches.match(event.request).then(function(response) {
      // 如果找到了匹配的响应，则返回缓存的视频
      return response || fetch(event.request);
      // 注意：如果请求不在缓存中，仍然尝试从网络获取
    })
  );
});
```

#### 实践案例
例如，假设我在开发一个教育类的PWA，其中包含了数个教学视频。为了优化用户体验，我会在用户初次访问应用时缓存所有的教学视频。当用户处于无网络环境（如飞行模式时）或网络不稳定时，他们仍能够通过 Service Worker 访问这些离线视频，无需担心中断学习。这不仅提升了用户体验，还减轻了服务器的负担，尤其是在高流量时期。

#### 结论
通过实现以上步骤，PWA 可以有效支持离线视频内容，大大增强应用的可用性和用户满意度。这种方法特别适用于视频内容重的应用如在线课程、培训模块等，确保用户即使在离线状态也能够继续他们的学习和娱乐活动。

How to offline video content using PWA?

在 Progressive Web Apps (PWA) 中，控制何时显示安装提示是一个重要环节，可以帮助提升用户体验。通常，浏览器会在满足特定条件时自动触发 `beforeinstallprompt` 事件，但是如果用户第一次拒绝了安装，之后想要重新触发这个提示，就需要手动操作。

### 重新触发安装提示的步骤：

1. **捕获并存储事件**:
    在初次触发 `beforeinstallprompt` 事件时，不要直接调用 `prompt()` 方法，而是将事件存储起来以备后用。例如：
    ```javascript
    let deferredPrompt;

    window.addEventListener('beforeinstallprompt', (e) => {
      // 阻止默认处理，延迟显示安装提示
      e.preventDefault();
      deferredPrompt = e;
      // 更新UI或显示某些按钮以提示用户可以安装PWA
    });
    ```

2. **提供一个触发机制**:
    提供一个用户可以触发的操作，例如按钮点击，来重新显示安装提示。当用户执行该操作时，使用之前存储的 `beforeinstallprompt` 事件。
    ```javascript
    button.addEventListener('click', (e) => {
      // 显示安装提示
      if (deferredPrompt) {
        deferredPrompt.prompt();
        deferredPrompt.userChoice.then((choiceResult) => {
          if (choiceResult.outcome === 'accepted') {
            console.log('用户接受安装');
          } else {
            console.log('用户拒绝安装');
          }
          deferredPrompt = null;
        });
      }
    });
    ```

3. **监听用户决策**:
    在调用 `prompt()` 方法后，你可以通过 `userChoice` 属性来得知用户的选择是接受安装还是拒绝安装，并据此更新应用的用户界面或状态。

### 注意事项：

- 确保不要在应用加载时立即询问用户是否安装，这可能会被视为侵扰，影响用户体验。
- 提供一个适当的时机和理由来引导用户安装，比如当他们已经使用了一段时间应用，并且显示出了兴趣。
- 一旦用户拒绝了安装，原生的 `beforeinstallprompt` 事件可能就不会再自动触发了，因此需要通过上述方法来人工触发。

通过这种方式，即使用户最初拒绝了安装，我们也能在他们准备好时，提供一个再次触发安装的机会。

How to retrigger beforeinstallprompt in PWA?

在实现Web推送功能之前，进行特征检测是非常重要的步骤，这可以确保我们的网页应用能够在不支持该功能的浏览器上优雅退化，同时在支持的环境中提供推送通知服务。

### 1. 检测浏览器对Service Worker的支持
首先，Web推送通知依赖于Service Workers来在后台处理推送事件。因此，我们需要检测浏览器是否支持Service Workers。这可以通过检查`navigator`对象中是否存在`serviceWorker`属性来实现：

```javascript
if ('serviceWorker' in navigator) {
  // 支持Service Worker
  console.log('此浏览器支持Service Worker');
} else {
  // 不支持Service Worker
  console.log('此浏览器不支持Service Worker');
}
```

### 2. 检测浏览器对Push API的支持
即使浏览器支持Service Workers，也不一定支持推送功能。为了确定浏览器是否支持Push API，我们需要检查`PushManager`在`window`对象中是否存在：

```javascript
if ('PushManager' in window) {
  // 支持Push API
  console.log('此浏览器支持Push API');
} else {
  // 不支持Push API
  console.log('此浏览器不支持Push API');
}
```

### 3. 检测浏览器对通知的支持
除了推送通知，我们还需要检查浏览器是否支持桌面通知，这通常通过`Notification` API实现。可以通过如下方式来检测：

```javascript
if ('Notification' in window) {
  // 支持通知
  console.log('此浏览器支持桌面通知');
} else {
  // 不支持通知
  console.log('此浏览器不支持桌面通知');
}
```

### 4. 综合检测
在实际应用中，我们通常会将上述检测结合起来，只有当所有必要特性都被支持时，我们才启用推送通知功能。可以通过一个综合功能检测函数来实现：

```javascript
function checkPushNotificationSupport() {
  if ('serviceWorker' in navigator && 'PushManager' in window && 'Notification' in window) {
    console.log('此浏览器支持所有推送通知所需特性');
    return true;
  } else {
    console.log('此浏览器不支持一项或多项推送通知所需特性');
    return false;
  }
}

// 使用该函数
if (checkPushNotificationSupport()) {
  // 初始化推送通知相关功能
  // 如注册Service Worker，请求用户授权等
} else {
  // 可以提供用户反馈或退化方案
}
```

### 例子
在我之前的项目中，我们使用上述方法来在Web应用启动时检测推送功能的支持情况。如果所有检测都通过，我们会进一步请求用户的推送订阅权限，然后注册Service Worker来处理推送事件。如果检测不通过，我们会通知用户该功能不可用，并记录不支持的具体原因以便后续改进。

特征检测不仅提升了应用的健壮性，也保证了用户体验的一致性，即在不同的浏览器环境下都能得到适当的服务或提示。

How to do feature detection for Web Push?

要清除 Firefox 中的 Service Worker 缓存，可以按照以下步骤进行：

1. **打开开发者工具**：
   - 你可以通过点击菜单（通常在浏览器窗口右上角的三条横线），选择“Web Developer”，然后点击“Toggle Tools”，或者直接使用快捷键`Ctrl + Shift + I`（在 macOS 上是`Command + Option + I`）来打开开发者工具。

2. **进入 Service Workers 选项卡**：
   - 在开发者工具窗口中，找到并点击“Application”或“Storage”选项卡。具体名称可能会因 Firefox 版本不同而有所变化。

3. **查找 Service Worker**：
   - 在“Application”或“Storage”选项卡中，找到“Service Workers”选项。这里会列出所有当前域名下活跃的 Service Workers。

4. **注销 Service Worker**：
   - 你可以看到每个 Service Worker 的状态，包括它的脚本URL、当前状态（激活、等待中、或者停止）。要移除 Service Worker，可以点击“Unregister”按钮。这将注销 Service Worker，并清除它的缓存。

5. **清除站点数据**：
   - 如果你想彻底清除所有缓存，包括由 Service Workers 创建的缓存，可以在开发者工具里面找到“Clear site data”按钮。点击此按钮会清除掉所有的数据，包括缓存、Cookies、IndexedDB 等。

6. **确认 Service Worker 已被移除**：
   - 在注销 Service Worker 之后，刷新页面或者关闭再重新打开开发者工具，以确保 Service Worker 已经被完全移除。

这些步骤适用于开发者或者高级用户，他们希望在进行网站开发或调试时管理 Service Workers。普通用户如果想清除缓存，可以通过“Preferences”（偏好设置）> “Privacy & Security”（隐私与安全）> “Cookies and Site Data”（Cookies 和站点数据）> “Clear Data”（清除数据）来清除网站数据，但这种方法并不专门针对 Service Workers。

作为一个例子，假设你正在开发一个渐进式网络应用（PWA），并且你刚刚更新了 Service Worker 的脚本。为了确保新的 Service Worker 脚本被安装和激活，你可能需要按照上述步骤清除旧的 Service Workers 和缓存。这确保了应用能够加载最新的文件，并按预期工作。

How to clear a Service Worker cache in Firefox?

在强制刷新或更新Service Worker时，通常涉及以下几个步骤：

1. **更新Service Worker文件**：
   确保你已经对Service Worker脚本做了修改。即便是很小的改动，如更新文件中的注释，也能触发Service Worker的更新事件，因为浏览器会检查Service Worker文件是否有字节级别的变化。

2. **Service Worker生命周期利用**：
   Service Worker的生命周期中有一个`install`事件。当检测到Service Worker文件有更新时，新的Service Worker将会进入`install`阶段。在这个阶段，你可以清除旧缓存并且执行新的缓存逻辑。

3. **激活新的Service Worker**：
   在新的Service Worker安装后，它会进入`wait`状态。你可以通过调用`self.skipWaiting()`方法来强制当前正在等待的Service Worker立即进入`activate`状态。

4. **更新客户端**：
   新的Service Worker激活后，并不会控制当前打开的页面，直到下次用户访问。为了让新的Service Worker立即接管，可以使用`clients.claim()`方法。

5. **通知用户**：
   如果你希望用户知道有一个新版本可用，并且鼓励他们刷新页面来使用新的Service Worker，可以在页面上显示一个通知或者按钮来提示用户。

### 示例代码

以下是一个简单的Service Worker更新流程实例：

```javascript
// 在Service Worker文件中
self.addEventListener('install', event => {
  // 强制当前正在等待的Service Worker立即进入activate状态
  self.skipWaiting();
});

self.addEventListener('activate', event => {
  // 让新的Service Worker立即接管当前页面
  event.waitUntil(clients.claim());
  // 清理旧版本缓存的逻辑
});
```

```javascript
// 在注册Service Worker的主文件中
if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/service-worker.js').then(reg => {
    reg.addEventListener('updatefound', () => {
      const newWorker = reg.installing;
      newWorker.addEventListener('statechange', () => {
        if (newWorker.state === 'installed' && navigator.serviceWorker.controller) {
          // 新的Service Worker已经就绪，可以通知用户刷新页面了
          // 这里可以显示一个“更新可用”的通知或者刷新按钮
        }
      });
    });
  });
}
```

### 强制刷新页面

如果你控制了页面逻辑，你甚至可以在新的Service Worker激活后自动刷新页面，但这通常不是一个好的做法，因为用户可能会丢失未保存的状态。

你可以这样做：

```javascript
if ('serviceWorker' in navigator) {
  navigator.serviceWorker.addEventListener('controllerchange', () => {
    // 当新的Service Worker取得控制权时，刷新页面
    window.location.reload();
  });
}
```

请注意，强制刷新页面可能导致用户体验问题，因此确保在适当的时机执行该操作，例如，当用户完成他们的工作并且页面可以安全地刷新时。

这些步骤和代码示例展示了如何在更新Service Worker时保持页面的正常运作并及时地将更新推送给用户。在实际应用中，会根据具体的业务需求和更新策略来调整这个流程。

As the previous answers stated, there is a 1 day (24hr) built-in limit for the browser to look for updates to the service worker, but what you need to be mindful of is you still need to call `.update()` on your `ServiceWorkerRegistration` object otherwise the original version of the file will be used.

While testing changes in Chrome, I always right-click on the refresh button and select 'Empty Cache and Hard Reset' (options are available when developer tools are open) when working on my service worker script.

'sw-precache' has been superseded by [Workbox](https://workboxjs.org/) which generates hashes for the files you want to precache and adds those to the source code of your service worker (I don't know if `sw-precache` works the same way, Jeff's answer suggests it does). If any of the files you want to precache change -- and you re-run your build -- the updated hashes in your service worker are updated which pretty much guarantees the service worker will be "at least one byte different".

When you reload (`ctrl-r`) or re-visit your app the browser will fetch again the service worker that was registered for it. And, if that service worker has changed, it will be "queued up" to manage the app. But it won't start managing the app until you close all tabs with the app open, and then open a new one.

When you hard refresh (`shift-ctrl-r`) [it’ll always load without a controller](https://github.com/w3c/ServiceWorker/blob/master/explainer.md#so-im-controlling-pages-now) which is not the same as using your new service worker.

For testing during development, I use [skip waiting](https://developers.google.com/web/fundamentals/primers/service-workers/lifecycle#skip_waiting) in devtools to make the new service worker replace the old one without waiting for me to close all the tabs.

If one file's hash changes, that's enough to ensure that the service worker JavaScript file generated by `sw-precache` changes. That, in turn, is enough to trigger the service worker update flow.

If you're not seeing an update flow triggered while testing things out, then it may be due to the service worker JavaScript file being served with HTTP caching headers that cause it to be fetched from the browser's cache rather than the from the network.

See [https://stackoverflow.com/a/38854905/385997](https://stackoverflow.com/a/38854905/385997) for a discussion of how HTTP caching headers come into play, and the best practices with regards to that.

One option that I have implemented from a UX standpoint is calling the unregister method on your service worker. ([https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerRegistration/unregister](https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerRegistration/unregister))

Once the unregister process is complete you can:

1.  force the window to refresh (window.location.reload)
2.  Based on your load up process, you can fetch the new service worker which will hopefully cache all your new content.

I have ran into weird issues with the service worker before, so this type of solution allows you to somewhat clear the old cache and refresh the state of your application without forcing users to clear their actual browser cache, while at the same time reloading your application.

EX (How to Unregister):

    serviceworker.unregister()
        .then( unregResult => { 
           //You can check if successful with Promise result 'unregResult'
           window.location.reload();
        })

Store a version number in `service‑worker.js`
=============================================

**A one-character change** in the controlling `service-worker.js` will automatically trigger a PWA update. Hence, if you store the version number in a `const` in this file and change it, an update of the PWA will be triggered.

How the update eventually is handled, is determined by the `service-worker.js`. Different update strategies may be defined in terms of the size and volatility of the PWA assets.

However, there is one **important caveat.** Make sure that the **browser cache expiry directive** set by the `.htaccess` file on your asset server is set to a really short duration (e.g. `hours`) or even to [**none**](https://stackoverflow.com/a/66756683/2192488). Failing to do so, will result in the browser not seeing any change for days to come in the `manifest.json`, nor the `service-worker.js`.

More details about service worker behaviour are available from [Google Web Fundamentals](https://developers.google.com/web/fundamentals/primers/service-workers/lifecycle).

当您希望建立一个新版本的 Service Worker 并替换掉旧版本时，您需要确保新的 Service Worker 可以被安装并且激活，从而更新用户的页面。这个过程通常涉及以下步骤：

1. **更新 Service Worker 文件：** 为了触发 Service Worker 的更新检查，你需要对 Service Worker 的脚本文件做出一些变化。浏览器会比较 Service Worker 文件的字节码来决定是否需要安装一个新版本。

2. **安装新的 Service Worker：** 当浏览器检测到 Service Worker 文件有变化时，它会尝试安装新的 Service Worker。安装过程通常在 `install` 事件中完成。

3. **等待新的 Service Worker 激活：** 默认情况下，新的 Service Worker 在安装后不会立即激活，因为旧的 Service Worker 可能还在控制着当前页面。新的 Service Worker 会处于 waiting 状态，直到当前所有的页面都关闭，它才会被激活。

4. **加速激活过程：** 如果您想要强制新的 Service Worker 立即接管，您可以在新的 Service Worker 中使用 `self.skipWaiting()`，这样它就可以跳过等待直接进入激活状态。

5. **更新客户端页面：** 一旦新的 Service Worker 激活，旧的客户端（页面）需要被更新。可以在新的 Service Worker 的 `activate` 事件中使用 `clients.claim()` 来实现。这将允许新的 Service Worker 立即控制所有客户端。

这里是一个简单的例子，展示了如何在 Service Worker 脚本中使用 `skipWaiting` 和 `clients.claim`：

```javascript
self.addEventListener('install', function(event) {
  // 执行安装步骤
  event.waitUntil(
    // 缓存资源等操作
    self.skipWaiting() // 强制进行 Service Worker 更新
  );
});

self.addEventListener('activate', function(event) {
  event.waitUntil(
    clients.claim() // 让新的 Service Worker 接管页面
  );
});
```

为了从页面脚本中强制刷新 Service Worker，你可以使用以下步骤：

1. 注册 Service Worker（如果尚未注册）。
2. 监听 Service Worker 的更新。
3. 当检测到更新时，可以用 `postMessage` API 发送消息给 Service Worker，要求其强制更新。

例如：

```javascript
if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/service-worker.js').then(reg => {
    reg.addEventListener('updatefound', () => {
      const newWorker = reg.installing;
      newWorker.addEventListener('statechange', () => {
        if (newWorker.state === 'installed' && navigator.serviceWorker.controller) {
          // 通知新的 Service Worker 接管控制权
          newWorker.postMessage({ action: 'SKIP_WAITING' });
        }
      });
    });
  });
}

// Service Worker 文件中
self.addEventListener('message', (event) => {
  if (event.data.action === 'SKIP_WAITING') {
    self.skipWaiting();
  }
});
```

这样，您就可以强制刷新/更新 Service Worker 了。记住，虽然可以强制更新 Service Worker，但最好还是确保这样做对用户来说是平滑且不会导致数据丢失的。

对于Service Worker的强制刷新或更新，以下是步骤和考虑事项：

1. **更新 Service Worker 文件**：
   要使浏览器检查更新的 Service Worker，你需要更改 Service Worker 文件 (`service-worker.js` 或任何你命名的文件) 的内容。即使是一个简单的空格或注释的变化，都会导致浏览器认为 Service Worker 已经更新。

2. **Service Worker 生命周期**：
   Service Worker 有一个内建的生命周期，用于管理安装和更新。当一个新的 Service Worker 被检测到，且与现有 Service Worker 不同时，它会进入 `install` 阶段，但不会立即控制页面，而是等待 `activate` 阶段。

3. **跳过等待（Skip Waiting）**：
   默认情况下，新的 Service Worker 会在等待状态，直到所有加载了旧 Service Worker 的页面关闭。为了让新的 Service Worker 立即接管，你可以在 Service Worker 文件中添加 `self.skipWaiting()`，这样新的 Service Worker 在安装结束后会立即进入激活状态。

    ```javascript
    // 在 Service Worker 的 'install' 事件中
    self.addEventListener('install', event => {
        event.waitUntil(
            // 强制进行更新
            self.skipWaiting()
        );
    });
    ```

4. **客户端的 Claim**：
   一旦激活，新的 Service Worker 应该开始接管控制页面。但是，如果你想让 Service Worker 立即控制所有客户端，包括加载旧 Service Worker 的页面，可以使用 `self.clients.claim()` 方法。

    ```javascript
    // 在 Service Worker 的 'activate' 事件中
    self.addEventListener('activate', event => {
        event.waitUntil(
            self.clients.claim()
        );
    });
    ```

5. **更新客户端页面**：
   即使新的 Service Worker 激活并开始控制页面，你也可能需要刷新页面，以确保新的 Service Worker 接管并应用新的缓存策略或其他更新。你可以通过以下方式通知用户刷新页面，或者在某些情况下可以强制刷新。

    ```javascript
    // 通常，你可以提醒用户重新加载页面
    if (navigator.serviceWorker) {
        navigator.serviceWorker.addEventListener('controllerchange', () => {
            // 在这里通知用户或刷新页面
            console.log('Service Worker 已更新。');
            window.location.reload();
        });
    }
    ```

6. **更新缓存**：
   更新了 Service Worker 后，你还需要更新缓存的资源。你可以在 `install` 事件中通过删除旧缓存的方式来做到这一点。

    ```javascript
    self.addEventListener('install', (event) => {
        event.waitUntil(
            caches.keys().then(cacheNames => {
                return Promise.all(
                    cacheNames.map(cache => {
                        if (cache !== currentCacheName) {
                            // 删除旧缓存
                            return caches.delete(cache);
                        }
                    })
                );
            })
        );
    });
    ```

通过使用以上技术，你可以确保 Service Worker 的更新能够快速且强制地推送到客户端，这对于紧急修复错误或推出新功能尤为重要。记住，Service Worker 的更新可能涉及对用户体验的中断，所以应该在用户不太可能被中断的时候进行更新，或者确保前端有相应的提醒和用户引导措施。

How to force service worker to update？

注册 Service Worker 可能会因为多种原因失败，以下是一些常见的原因及其解释：

### 1. 作用域问题（Scope）
Service Worker 的作用域由其注册时的位置决定。如果你尝试在子目录注册一个 Service Worker，而这个 Service Worker 的作用域是在更高级别的目录，那么注册可能会失败。例如，试图在 `/pages/` 下注册一个 Service Worker，但其作用域是 `/`，浏览器将不会允许这么做。

**例子**：
```javascript
// 假设在 /pages/index.html 中
navigator.serviceWorker.register('/service-worker.js', { scope: '/' })
.then(function(registration) {
  // 注册成功
})
.catch(function(error) {
  // 注册失败，可能是由于作用域问题
});
```

### 2. 路径错误
如果 Service Worker 文件的路径不正确，浏览器无法找到 Service Worker 脚本，也会导致注册失败。

**例子**：
```javascript
// 假设实际的 Service Worker 位于 /scripts/service-worker.js
navigator.serviceWorker.register('/wrong-path/service-worker.js')
.then(function(registration) {
  // 注册成功
})
.catch(function(error) {
  // 注册失败，因为路径不正确
});
```

### 3. 不支持 Service Worker
并非所有的浏览器都支持 Service Worker，尝试在不支持 Service Worker 的浏览器中注册它，自然会失败。

**例子**：
```javascript
if ('serviceWorker' in navigator) {
  // 浏览器支持 Service Worker
  navigator.serviceWorker.register('/service-worker.js')
  .then(function(registration) {
    // 注册成功
  })
  .catch(function(error) {
    // 注册失败
  });
} else {
  // 浏览器不支持 Service Worker
  console.log('Service Worker is not supported by this browser.');
}
```

### 4. 服务工作线程文件中的错误
如果 Service Worker 文件本身存在语法错误或其他问题，它的注册也会失败。

**例子**：
```javascript
// service-worker.js 文件中的语法错误
self.addEventListener('fetch', function(event) {
  // 缺少了闭合的花括号
```

### 5. HTTPS 协议
出于安全原因，Service Worker 只能在 HTTPS 协议下注册成功（除了本地环境，如 `localhost`，可以使用 HTTP）。如果你在非安全的 HTTP 环境下尝试注册 Service Worker，注册将失败。

**例子**：
```javascript
// 尝试在 HTTP 环境下注册 Service Worker
navigator.serviceWorker.register('/service-worker.js')
.then(function(registration) {
  // 注册成功
})
.catch(function(error) {
  // 注册失败，因为不是 HTTPS 环境
});
```

### 6. 浏览器隐私模式
某些浏览器在隐私模式下可能不允许使用 Service Worker，因此尝试在这种模式下注册可能会失败。

### 7. 过时的浏览器缓存
如果浏览器缓存了旧的 Service Worker 文件或注册代码，可能导致注册看似失败，这时候清除缓存可能会解决问题。

针对上述任何注册失败的情况，开发者都应该通过浏览器的开发者工具检查错误信息，以便找到具体的失败原因并解决。通常，注册失败时的 catch 代码块可以获取到错误信息，这对于调试非常有用。

Why service worker registration failed?

Service Worker 控制台通常指的是浏览器开发者工具中与 Service Worker 相关的部分，它允许开发者管理、调试和了解 Service Worker 的状态和行为。Service Worker 是一种运行在浏览器背后、独立于网页的 JavaScript Worker，它可以用来处理离线缓存、推送通知和背景数据同步等功能。

在 Google Chrome 浏览器中，可以通过以下步骤访问 Service Worker 控制台：

1. 打开 Chrome 浏览器。
2. 访问一个使用了 Service Worker 的网站。
3. 右键点击页面，选择“检查”（Inspect），或者使用快捷键`Ctrl+Shift+I`（Windows/Linux）或`Cmd+Opt+I`（Mac）来打开开发者工具。
4. 在开发者工具窗口中，选择“Application”面板。
5. 在“Application”面板的左侧菜单中，找到并点击“Service Workers”。

在这个部分，你可以看到当前网站注册的所有 Service Workers 的信息，包括它们的状态（激活、运行中、停止）、作用域（scope）、以及是否处于调试状态。此外，你还可以对 Service Workers 进行一些操作，比如更新、停止或者删除 Service Worker，或者模拟离线状态来测试 Service Worker 的离线行为。

例如，如果我为我的网站开发了一个 Service Worker 来缓存静态资源，当用户第一次访问网站时，Service Worker 会被安装并激活，之后它会根据预定义的缓存策略缓存一些静态资源。当用户在没有网络连接的情况下再次访问网站时，即使处于离线状态，网站依然可以通过 Service Worker 提供那些已经缓存的资源，从而提升用户体验。

总的来说，Service Worker 控制台是 Chrome 开发者工具中一个非常有用的部分，它为开发者提供了强大的功能来管理和调试 Service Worker。

Go to chrome://serviceworker-internals

Choose any service worker and start it if not already started.

Click on Inspect!!

Boom! You have the console there!

If a page has a service worker, then that service worker's logs show in that page's JavaScript console. You can see the source of a log line on the right-hand side of the log:

[![log line sources](https://i.stack.imgur.com/aKNa3.png)](https://i.stack.imgur.com/aKNa3.png)

In the console, there is a select box to select the _JavaScript context_. This defaults to `top` (which means "show everything"), but you can select a more specific context for just the service worker:

[![selecting alternative context](https://i.stack.imgur.com/HhTQx.png)](https://i.stack.imgur.com/HhTQx.png)

Service Worker 控制台通常指的是开发者工具中与 Service Worker 相关的部分，它可以让开发者查看和管理 Service Workers 的状态、生命周期、以及相关的事件和数据。Service Worker 是一种运行在浏览器背后的脚本，它可以帮助实现离线体验、消息推送和背景同步等功能。

要在 Chrome 浏览器中找到与 Service Worker 相关的控制台，您可以按照以下步骤操作：

1. 打开 Chrome 浏览器。
2. 访问您想要检查 Service Worker 的网站。
3. 点击右上角的三个点按钮，选择“更多工具”，然后在下拉菜单中选择“开发者工具”。也可以直接使用快捷键 `Ctrl+Shift+I`（Windows/Linux）或 `Cmd+Option+I`（Mac）来打开开发者工具。
4. 在开发者工具窗口中，点击上方的“Application”（应用）标签。如果看不到“Application”，可能需要点击“>>”符号来展开隐藏的标签列表。
5. 在左侧的导航栏中，找到并点击“Service Workers”选项。在这里，您可以看到当前活动的 Service Workers，包括它们的状态、脚本URL、是否被控制的页面等信息。
6. 在“Service Workers”选项下，您可以看到诸如“Offline”（离线模式）、“Update on reload”（重新加载时更新）等选项，这些选项可以帮助测试和调试 Service Workers。

例如，如果您正在开发一个支持离线功能的网页应用，您可能会在 Service Worker 中编写代码来缓存某些资源。然后，您可以在 Service Worker 控制台中模拟离线状态，来测试您的网页在没有网络连接时是否能够正确地从缓存中加载资源。

这些工具对于开发者来说非常有用，因为它们可以帮助确保 Service Workers 正确安装、激活、运行，并且能够处理各种事件，从而提升网页应用的性能和用户体验。

Service Worker 控制台是开发者工具（Developer Tools）的一部分，是 Google Chrome 浏览器提供的一个界面，用于检查和管理网页或应用中的 Service Workers。Service Worker 是一种运行在浏览器背后的脚本，可以帮助实现离线体验、消息推送和背景同步等功能。它作为一个独立的线程运行，不依赖于网页直接控制，因此可以在不打开网页的情况下执行任务。

在 Chrome 浏览器中，您可以通过以下步骤访问 Service Worker 控制台：

1. 打开 Chrome 浏览器。
2. 访问您想要检查的网站。
3. 右键点击页面，选择“检查”（或使用快捷键 Ctrl+Shift+I / Cmd+Option+I 打开开发者工具）。
4. 在开发者工具中，切换到“Application”选项卡。
5. 在左侧导航菜单中，找到并展开“Service Workers”部分。

在这里，您可以看到当前域下注册的所有 Service Workers 的详细信息，包括它们的状态（例如，已激活、正在运行或已停止）、作用域、脚本URL、以及是否被控制的页面。您还可以对 Service Workers 进行管理，例如更新、卸载、启用离线功能或者调试 Service Workers。

例如，如果我在开发一个渐进式网络应用（PWA），我会使用 Service Worker 来缓存关键资产，以确保我的应用即使在离线状态下也能提供核心功能。在实施缓存策略后，我会通过 Service Worker 控制台检查 Service Worker 的状态，确保它已正确注册并激活，以及验证缓存行为是否符合预期。

What is service worker console and where is it in chrome browser?

在页面刷新时激活更新后的service worker，通常涉及以下几个步骤：

1. **注册Service Worker：**
   首先，需要在你的网页中注册service worker。这通常在JavaScript的主文件中进行：

   ```javascript
   if ('serviceWorker' in navigator) {
     window.addEventListener('load', function() {
       navigator.serviceWorker.register('/service-worker.js').then(function(registration) {
         // 注册成功
         console.log('ServiceWorker registration successful with scope: ', registration.scope);
       }, function(err) {
         // 注册失败
         console.log('ServiceWorker registration failed: ', err);
       });
     });
   }
   ```

2. **更新Service Worker文件：**
   当你更新了service worker的JavaScript文件（`service-worker.js`），浏览器会检测到文件内容的变化，这时候新的service worker会开始安装流程，但此时不会立即激活。

3. **Install和Activate事件：**
   在service worker文件内部，你可以监听`install`和`activate`事件。新的service worker在安装后通常会进入等待状态，直到所有的客户端（页面）都关闭，然后才会被激活。

   ```javascript
   self.addEventListener('install', event => {
     // 执行安装步骤
   });

   self.addEventListener('activate', event => {
     // 在激活时，通常会清理旧的缓存等
     event.waitUntil(
       // 清理工作
     );
   });
   ```

4. **立即激活新的Service Worker：**
   若要在页面刷新时立即激活新的service worker，可以利用`self.skipWaiting()`方法。在`install`事件中调用这个方法可以使新的service worker跳过等待阶段，直接进入激活状态。

   ```javascript
   self.addEventListener('install', event => {
     event.waitUntil(
       // 安装步骤例如缓存文件等，
       // 然后调用skipWaiting来立即激活service worker
       self.skipWaiting()
     );
   });
   ```

5. **控制页面：**
   即使service worker已经激活，如果页面在安装新的service worker之前就已经打开了，那么你还需要通过`clients.claim()`在activate事件中获取对其控制权。

   ```javascript
   self.addEventListener('activate', event => {
     event.waitUntil(
       clients.claim() // 这个操作会使新的service worker立即控制所有的页面
     );
   });
   ```

6. **页面刷新：**
   你可以在页面上提供一个机制来刷新页面，或者通过service worker通知用户，并使用`window.location.reload()`来刷新页面以使用更新后的service worker。

   ```javascript
   navigator.serviceWorker.addEventListener('controllerchange', () => {
     window.location.reload();
   });
   ```

7. **确保更新的Service Worker被应用：**
   对于已经打开的页面，为了立即应用新的service worker，你可能需要提醒用户刷新页面，或者使用前面提到的`window.location.reload()`强制刷新。

通过以上步骤，页面刷新后，更新后的service worker可以被激活并立即开始控制页面。不过，请注意，强制刷新用户的页面可能会导致用户体验不佳，因此应当谨慎使用。

There are conceptually two kinds of updates, and it isn't clear from your question which we're talking about, so I'll cover both.

Updating content
================

Eg:

*   The text of a blog post
*   The schedule for an event
*   A social media timeline

These will likely be stored in the cache API or IndexedDB. These stores live independently of the service worker - updating the service worker shouldn't delete them, and updating them shouldn't require an update to the service worker

Updating the service worker is the native equivalent of shipping a new binary, you shouldn't need to do that to (for example) update an article.

When you update these caches is entirely up to you, and they aren't updated without you updating them. I cover a number of patterns in the [offline cookbook](https://jakearchibald.com/2014/offline-cookbook/), but [this is my favourite one](https://jakearchibald.com/2014/offline-cookbook/#cache-then-network):

1.  Serve page shell, css & js from a cache using the service worker.
2.  Populate page with content from the cache.
3.  Attempt to fetch content from the network.
4.  If the content is fresher than what you have in the cache, update the cache and the page.

In terms of "update the page", you need to do that in a way that isn't disruptive to the user. For chronological lists this is pretty easy, as you just add the new stuff to the bottom/top. If it's updating an article it's a bit trickier, as you don't want to switch text from underneath the user's eyes. In that case it's often easier to show some kind of notification like "Update available - **show update**" which, when clicked, refreshes the content.

[Trained to thrill](https://jakearchibald.github.io/trained-to-thrill/) (perhaps the first ever service worker example) demonstrates how to update a timeline of data.

Updating the "app"
==================

This is the case where you _do_ want to update the service worker. This pattern is used when you're:

*   Updating your page shell
*   Updating JS and/or CSS

If you want the user to get this update in a non-atomic, but fairly safe way, there are patterns for this too.

1.  Detect updated service worker "waiting"
2.  Show notification to user "Update available - **update now**"
3.  When the user clicks this notification, postmessage to the service worker, asking it to call `skipWaiting`.
4.  Detect the new service worker becoming "active"
5.  `window.location.reload()`

Implementing this pattern is part of my [service worker Udacity course](https://www.udacity.com/course/offline-web-applications--ud899), and [here's the diff of the code before/after](https://github.com/jakearchibald/wittr/compare/task-update-notify...update-interaction).

You can take this further too. For example, you could employ some kind of semver-esque system, so you know the version of the service worker the user currently has. If the update is minor you may decide calling `skipWaiting()` is totally safe.

I wrote a blog post explaining how to handle this. [https://redfin.engineering/how-to-fix-the-refresh-button-when-using-service-workers-a8e27af6df68](https://redfin.engineering/how-to-fix-the-refresh-button-when-using-service-workers-a8e27af6df68)

I also have a working sample on github. [https://github.com/dfabulich/service-worker-refresh-sample](https://github.com/dfabulich/service-worker-refresh-sample)

There are four approaches:

1.  **`skipWaiting()` on installation.** This is dangerous, because your tab can get a mix of old and new content.
2.  **`skipWaiting()` on installation, and refresh all open tabs on `controllerchange`** Better, but your users may be surprised when the tab randomly refreshes.
3.  **Refresh all open tabs on `controllerchange`; on installation, prompt the user to `skipWaiting()` with an in-app "refresh" button.** Even better, but the user has to use the in-app "refresh" button; the browser's refresh button still won't work. This is documented in detail in [Google's Udacity course on Service Workers](https://www.udacity.com/course/offline-web-applications--ud899) and the [Workbox Advanced Guide](https://developers.google.com/web/tools/workbox/guides/advanced-recipes#offer_a_page_reload_for_users), as well as the `master` branch of my [sample on Github](https://github.com/dfabulich/service-worker-refresh-sample).
4.  **Refresh the last tab if possible.** During fetches in `navigate` mode, count open tabs ("clients"). If there's just one open tab, then `skipWaiting()` immediately and refresh the only tab by returning a blank response with a `Refresh: 0` header. You can see a working example of this in the `refresh-last-tab` branch of my [sample on Github](https://github.com/dfabulich/service-worker-refresh-sample/tree/refresh-last-tab).

Putting it all together...

In the Service Worker:

    addEventListener('message', messageEvent => {
        if (messageEvent.data === 'skipWaiting') return skipWaiting();
    });
    
    addEventListener('fetch', event => {
        event.respondWith((async () => {
            if (event.request.mode === "navigate" &&
            event.request.method === "GET" &&
            registration.waiting &&
            (await clients.matchAll()).length < 2
            ) {
                registration.waiting.postMessage('skipWaiting');
                return new Response("", {headers: {"Refresh": "0"}});
            }
            return await caches.match(event.request) ||
            fetch(event.request);
        })());
    });
    

In the page:

    function listenForWaitingServiceWorker(reg, callback) {
        function awaitStateChange() {
            reg.installing.addEventListener('statechange', function () {
                if (this.state === 'installed') callback(reg);
            });
        }
        if (!reg) return;
        if (reg.waiting) return callback(reg);
        if (reg.installing) awaitStateChange();
        reg.addEventListener('updatefound', awaitStateChange);
    }
    
    // reload once when the new Service Worker starts activating
    var refreshing;
    navigator.serviceWorker.addEventListener('controllerchange',
        function () {
            if (refreshing) return;
            refreshing = true;
            window.location.reload();
        }
    );
    function promptUserToRefresh(reg) {
        // this is just an example
        // don't use window.confirm in real life; it's terrible
        if (window.confirm("New version available! OK to refresh?")) {
            reg.waiting.postMessage('skipWaiting');
        }
    }
    listenForWaitingServiceWorker(reg, promptUserToRefresh);

In addition to Dan's answer;

**1\. Add the `skipWaiting` event listener in the service worker script.**

In my case, a CRA based application I use [cra-append-sw](https://github.com/bbhlondon/cra-append-sw) to add this snippet to the service worker.

> **Note:** if you are using a recent version of `react-scripts`, the snippet below is [automatically added](https://github.com/GoogleChrome/workbox/issues/2394) and you won't need to use `cra-append-sw`.

    self.addEventListener('message', event => {
      if (!event.data) {
        return;
      }
    
      if (event.data === 'SKIP_WAITING') {
        self.skipWaiting();
      }
    });
    

**2\. Update register-service-worker.js**

For me, it felt natural to reload the page when the user navigates within the site. In the register-service-worker script I've added the following code:

    if (navigator.serviceWorker.controller) {
      // At this point, the old content will have been purged and
      // the fresh content will have been added to the cache.
      // It's the perfect time to display a "New content is
      // available; please refresh." message in your web app.
      console.log('New content is available; please refresh.');
    
      const pushState = window.history.pushState;
    
      window.history.pushState = function () {
        // make sure that the user lands on the "next" page
        pushState.apply(window.history, arguments);
    
        // makes the new service worker active
        installingWorker.postMessage('SKIP_WAITING');
      };
    } else {
    

Essentially we hook into the native `pushState` function so we know that the user is navigating to a new page. Although, if you also use filters in your URL for a products page, for example, you may want to prevent reloading the page and wait for a better opportunity.

Next, I'm also using Dan's snippet to reload all tabs when the service worker controller changes. This also will reload the active tab.

      .catch(error => {
        console.error('Error during service worker registration:', error);
      });
    
    navigator.serviceWorker.addEventListener('controllerchange', () => {
      if (refreshing) {
        return;
      }
    
      refreshing = true;
      window.location.reload();
    });

Even though the OP has disagreed with skipWaiting, skipWaiting is actually the correct solution for many apps, especially single page apps.

Open your precache in DevTools, check if there are any lazy loaded files. If there aren't - meaning everything in your precache are fetched immediately on page load, then it's safe to call skipWaiting, which will delete the old precache, replace with new assets (including the new index.html), waiting to be served on the next refresh. Since all the old assets are already in memory, which are running with the old index.html, there's nothing wo worry about.

(If you see a file in the precache but you aren't sure whether it's downloaded on page load, reload and watch the network traffic in DevTools yourself)

If you do have lazy loaded assets, then it indeed could cause a problem, but that's not a new problem created by service worker. Imagine your user opened a tab, then you deploy a new version, then the user clicks something which triggers a lazy load, but that asset is no longer on your server. This is an old problem. Precache unintentionally solved this problem, but you shouldn't rely on it, instead you should have your own exception handling logic, unless your app was designed to leverage the precache from the very beginning.

How to activate updated service worker on refresh

Service Worker 的作用域（Scope）定义了它能够控制的内容范围，即 Service Worker 可以拦截和处理哪些请求。作用域是通过 Service Worker 注册时指定的，一般来说，Service Worker 只能控制其注册所在路径和下级路径的请求。

例如，如果您在 `/app/` 路径下注册了一个 Service Worker，它的作用域将被限制在 `/app/` 及其子路径下。这意味着，Service Worker 可以拦截 `/app/`、`/app/home`、`/app/settings` 等路径的请求，但它无法控制 `/` 根路径或 `/other` 路径下的请求。

这个作用域的限定有助于确保 Service Worker 不会影响到其它不相关的页面和应用，提供了一种安全的方式来限制 Service Worker 的控制范围。

举个例子，如果一个在线商城网站在其根目录下注册了 Service Worker，并设置了根目录为作用域，那么这个 Service Worker 将能控制商城网站的所有页面。然而，如果商城网站希望仅仅对产品目录页面使用 Service Worker 来缓存和提供离线支持，那么它可以单独在 `/products/` 路径下注册一个 Service Worker，将作用域限制在这个子目录中。这样，Service Worker 只会影响 `/products/` 路径下的请求，而不会影响到其他页面。

Service workers are basically a proxy between your web application and the internet, so it can intercept calls to the network if so desired.

Scope in this instance refers to the path that the service worker will be able to intercept network calls from. The `scope` property can be used explicitly define the scope it will cover. However:

Service workers can only intercept requests originating in the scope of the current directory that the service worker script is located in and its subdirectories. [Or as MDN states](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API/Using_Service_Workers#Why_is_my_service_worker_failing_to_register):

> The service worker will only catch requests from clients under the service worker's scope.
> 
> The max scope for a service worker is the location of the worker.

As your service worker is located in `/static/mod/practice/`, it's not allowed to set its scope to `/practice/foopage/`. Requests to other hosts, e.g. `https://stackoverflow.com/foo`, can be intercepted in any case.

The easiest way to ensure that your service worker can intercept all the calls it needs to, would be to place it in the root directory of your web app (`/`). You can also override the default restrictions using an http header and manually setting the scope (see Ashraf Sabry's answer).

Leave the service worker file in whatever directory imposed by your project structure and set the `scope` option to `/` and add the `Service-Worker-Allowed` HTTP header to the response of your service worker file.

I'm using IIS, so I would add the following to web.config file:

    <location path="static/mod/practice/service-worker.js">
        <system.webServer>
            <httpProtocol>
                <customHeaders>
                    <add name="Service-Worker-Allowed" value="/" />
                </customHeaders>
            </httpProtocol>
        </system.webServer>
    </location>
    

And register the worker by:

    navigator.serviceWorker.register('/static/mod/practice/service-worker.js', { scope: '/' })
            .then(function (registration)
            {
              console.log('Service worker registered successfully');
            }).catch(function (e)
            {
              console.error('Error during service worker registration:', e);
            });
    

Tested on Firefox and Chrome.

Refer to the examples in [Service worker specification](https://w3c.github.io/ServiceWorker/#service-worker-script-response)

For the people who are using nginx it couldn't be any simpler:

    # Given that /static is your route to assets
    location /static {
            # using / as root scope
            add_header Service-Worker-Allowed /;
    ....

Just in case if the scope changes between development & production environment, as often we use local subdirectories for projects, using "./" for the scope may save the day (& make it dynamic).

    navigator.serviceWorker.register(
        `./service-worker.js`, 
        {
            scope: `./`
        }
    );

How to understanding service worker scope?

Service Worker 在 React JS 中是一个运行在浏览器背后的脚本，它不依赖于网页而独立工作，能够为应用提供不依赖网络的特性，比如离线内容的访问、背景同步和推送通知等。它相当于一个位于浏览器与网络之间的代理，可以截获和处理网络请求，以及根据需求管理缓存。

Service Worker 在 React 应用中的一个典型用途是创建渐进式网络应用（PWA）。PWA 是一种通过网络技术构建的应用程序，它可以提供类似原生应用的用户体验。通过使用 Service Worker，React 应用可以在用户的设备上缓存应用的核心文件，这样即使在没有网络连接的情况下，用户也能加载应用的基本界面和功能。

一个实际的例子是，当开发者使用 `create-react-app` 工具新建一个 React 项目时，生成的模板项目中自带了 Service Worker 的配置。这个配置默认是不启用的，但是开发者可以选择启用它，并根据实际需要对其进行配置，从而让应用具备 PWA 的特性。

启用 Service Worker 后，当用户首次访问 React 应用时，Service Worker 被安装并开始缓存应用的资源，如 HTML、CSS、JavaScript 文件和图片等。当用户再次访问该应用时，即使在离线状态下，Service Worker 也可以通过拦截请求并提供缓存的资源来加载应用。

Service Worker 还允许开发者通过编程方式精细控制缓存策略，例如决定哪些资源需要缓存、何时更新缓存、如何响应资源请求等。通过这种方式，可以优化应用的性能并提高用户体验。

You may not need a service worker for your application. If you are creating a project with create-react-app it is invoked by default

Service workers are well explained in this **[article](https://developers.google.com/web/fundamentals/primers/service-workers/)**. To Summarise from it

> A `service worker` is a script that your browser runs in the background, separate from a web page, opening the door to features that don't need a web page or user interaction. Today, they already include features like `push notifications` and `background sync` and have `ability to intercept and handle network requests`, including `programmatically managing a cache of responses`.
> 
> In the future, service workers might support other things like `periodic sync` or `geofencing`.

According to this **[PR to create-react-app](https://github.com/facebook/create-react-app/pull/1728)**

> `Service workers` are introduced with create-react-app via `SWPrecacheWebpackPlugin`.
> 
> Using a server worker with a cache-first strategy offers performance advantages, since the network is no longer a bottleneck for fulfilling navigation requests. It does mean, however, that developers (and users) will only see deployed updates on the "N+1" visit to a page, since previously cached resources are updated in the background.

The call to `register service worker` is enabled by default in new apps but you can always remove it and then you’re back to regular behaviour.

**In simple and plain words, it’s a script that browser runs in the background and has whatsoever no relation with web pages or the DOM, and provide out of the box features. It also helps you cache your assets and other files so that when the user is offline or on slow network.**

_Some of these features are proxying network requests, push notifications and background sync. Service workers ensure that the user has a rich offline experience._

You can think of the service worker as someone who sits between the client and server and all the requests that are made to the server pass through the service worker. Basically, a middle man. Since all the request pass through the service worker, it is capable to intercept these requests on the fly.

[![enter image description here](https://i.stack.imgur.com/ldRJk.png)](https://i.stack.imgur.com/ldRJk.png)

I'd like to add 2 important considerations about Service Workers to take into account:

1.  Service Workers require HTTPS. But to enable local testing, this restriction doesn't apply to `localhost`. This is for security reasons as a Service Worker acts like a _man in the middle_ between the web application and the server.
    
2.  With **Create React App** Service Worker is only enabled in the production environment, for example when running `npm run build`.
    

Service Worker is here to help developing a [Progressive Web App](https://web.dev/what-are-pwas/). A good resource about it in the context of Create React App can be found in their website [here](https://create-react-app.dev/docs/making-a-progressive-web-app/).

What is service worker in react js?

Service Worker 本身并不提供存储功能，但它常常与浏览器中的缓存 API 配合使用，来缓存应用资源。Service Worker 的缓存容量并不是由 Service Worker API 本身强制规定的，而是取决于浏览器的实现和用户设备的可用空间。

每个浏览器可能有不同的存储限制政策，并且这些政策可能会随着时间而改变。大多数现代浏览器都采用启发式方法动态管理每个原始站点（origin）的存储限额。通常，浏览器允许单个原始站点使用的存储量在几十到几百兆字节之间，这取决于用户设备上的总可用空间。

例如，Chrome 浏览器为所有网站的存储限制提供了一个动态配额，它通常是基于每个原始站点可用磁盘空间的一部分。这一部分可能在总磁盘空间的2-5%之间，但这个数字是不固定的，并且可能会根据不同的设备和用户的存储使用情况而变化。

为了给您一个实际的例子，假设用户设备上的可用空间为100GB，Chrome可能会为一个原始站点分配2GB作为最大存储限额。但请记住，这个限额是动态计算的，用户的存储使用情况和浏览器的策略会影响这个值。

总的来说，Service Worker 的缓存大小限制并不是固定不变的，它受多种因素影响，包括浏览器实现、设备存储容量、其他网站的存储使用情况等。开发者可以通过浏览器的配额管理 API 来检查可用存储量，并相应地管理缓存策略。

**Update Jan 15 2018**

The [StorageManager](https://developer.mozilla.org/en-US/docs/Web/API/StorageManager) interface of Storage API is becoming a standard for all storage related api queries. As mentioned by [@miguel-lattuada](https://stackoverflow.com/a/46933005/1657018), the [estimate API](https://developer.mozilla.org/en-US/docs/Web/API/StorageManager/estimate) would provide an estimate of the storage used a web app the available storage. Also, note the [QuotaExceededError](https://developer.mozilla.org/en-US/docs/Web/API/DOMException#exception-QuotaExceededError) exception which would help us in handling error scenarios.

eg code:

    if ('storage' in navigator && 'estimate' in navigator.storage) {
      navigator.storage.estimate().then(({usage, quota}) => {
        console.log(`Using ${usage} out of ${quota} bytes.`);
      }).catch(error => {
        console.error('Loading storage estimate failed:');
        console.log(error.stack);
      });
    } else {
      console.error('navigator.storage.estimate API unavailable.');
    }

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For more info, refer the following 2 great articles:

*   [MDN Web docs - Storage API](https://developer.mozilla.org/en-US/docs/Web/API/Storage_API)
*   [Google Developers: Estimating Available Storage Space](https://developers.google.com/web/updates/2017/08/estimating-available-storage-space)

* * *

**March 16 2017 (keeping it just for reference/history)**

Recently I came across this article: [offline-cookbook](https://jakearchibald.com/2014/offline-cookbook/#cache-persistence) which states as below:

Your **origin is given a certain amount of free space** to do what it wants with. That **free space is shared between all origin storage**: LocalStorage, IndexedDB, Filesystem, and of course Caches.

The **amount you get isn't spec'd**, it will differ depending on device and storage conditions. You can find out how much you've got via:

    navigator.storageQuota.queryInfo("temporary").then(function(info) {
       console.log(info.quota);
       // Result: <quota in bytes>
       console.log(info.usage);
       // Result: <used data in bytes>
    });
    

The above code [might not work in all the browsers](https://developer.mozilla.org/en-US/docs/Web/API/StorageQuota). (for eg: in chrome<48 one might have to look for webkitPersistentStorage etc)

**Other useful info/resources**

1.  As per [Offline Storage for Progressive Web Apps](https://medium.com/dev-channel/offline-storage-for-progressive-web-apps-70d52695513c#.19w8r1c4o) by Addy Osmani
    
    In `Chrome and Opera`: Your storage is per origin (rather than per API). Both storage mechanisms will store data until the browser quota is reached. Apps can check how much quota they’re using with the Quota Management API (as described above).
    
    `Firefox` no limits, but will prompt after 50MB data stored
    
    `Mobile Safari` 50MB max
    
    `Desktop Safari` unlimited (prompts after 5MB)
    
    `IE10+` maxes at 250MB and prompts at 10MB
    
2.  A more detailed guide on [Working with quota on mobile browsers](https://www.html5rocks.com/en/tutorials/offline/quota-research/) by Eiji Kitamura.
    

For now these are the most relevant articles/solutions found for my problem. If anyone knows some better article or specifications please share.

There's no explicit limit. All modern browsers are multi-process or similar, so a badly-designed page (or SW) won't do anything worse than crash itself.

Note that the SW spec is very explicit about the browser being able to kill and restart the SW at any time, for any reason. (If DevTools is open on a page, Chrome purposely kills SWs for the page constantly, to encourage you to adopt good practices.)

On latests browser you can use [StorageManager](https://developer.mozilla.org/en-US/docs/Web/API/StorageManager) which is an implementation of a new standard for browser storage, take a look at [this](https://developer.mozilla.org/en-US/docs/Web/API/Storage_API) mozilla article.

    let _storageStats = await navigator.storage.estimate();
    console.log(_storageStats);
    /*
      Will prompt something like this
      {quota: 15946471833, usage: 682}
      Which is a representation of quota/usage in bytes
      As you can see I get an insane quota of almost 16 GB
    */

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More info about `navigator.storage.estimate()` and `navigator.webkitTemporaryStorage.queryUsageAndQuota()` is here [https://developers.google.com/web/updates/2017/08/estimating-available-storage-space](https://developers.google.com/web/updates/2017/08/estimating-available-storage-space)

Testing page is here [https://thimbleprojects.org/startpolymer/361372/](https://thimbleprojects.org/startpolymer/361372/)

What is the storage limit for a service worker?

在 Progressive Web Application (PWA) 中，Service Worker 是一种运行在浏览器后台的脚本，负责管理缓存以及使应用能够在离线时工作。更新 Service Worker 管理的文件通常遵循以下流程：

### 文件更新流程：

1. **安装 Service Worker**：
   当用户首次访问 PWA 或者 Service Worker 文件 (`service-worker.js`) 有更新时，浏览器会尝试安装新的 Service Worker。这时，Service Worker 的 `install` 事件被触发。

2. **缓存新文件**：
   在 `install` 事件的处理函数中，通常会编写代码来打开缓存，并使用 `cache.addAll()` 方法缓存一个文件列表。此时，可以决定需要缓存哪些新文件或更新的文件。

3. **激活新的 Service Worker**：
   安装完成后，新的 Service Worker 会进入 `waiting` 状态。当网站上没有任何页面使用旧的 Service Worker 时，新的 Service Worker 会接收到 `activate` 事件。在 `activate` 事件的处理函数中，通常会清理旧缓存。

4. **管理旧缓存**：
   在激活阶段，可以通过比较缓存的版本来决定是否删除旧缓存中的文件，或者是整个旧缓存。这是通过 `caches.delete` 方法实现的。

5. **更新完成**：
   一旦新的 Service Worker 被激活并且旧缓存被清理，新的缓存开始生效，之后的网络请求都将通过新的 Service Worker 来处理。通过这个方式，文件得以更新。

### 何时更新：

- **Service Worker 文件变更**：
  每次用户访问 PWA 时，浏览器都会检查 Service Worker 文件是否有变更。如果检测到文件内容有一字节的改动，浏览器会认为 Service Worker 更新了，并开始上述的安装过程。

- **开发者触发更新**：
  开发者可以通过更改 Service Worker 文件，例如更新缓存文件的列表、修改缓存策略等来触发更新。开发者也可以通过版本号的方式来控制缓存的更新。

- **用户清空浏览器缓存**：
  如果用户清空了浏览器缓存，下次访问时 Service Worker 将会重新安装，意味着文件必须重新缓存。

### 示例：

在 Service Worker 的安装阶段，一个常见的更新文件的例子如下：

```javascript
const CACHE_NAME = 'cache-v1';
const URLS_TO_CACHE = [
  '/',
  '/styles/main.css',
  '/script/main.js'
];

self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(CACHE_NAME)
    .then((cache) => {
      console.log('Opened cache');
      return cache.addAll(URLS_TO_CACHE);
    })
  );
});

self.addEventListener('activate', (event) => {
  const cacheWhitelist = [CACHE_NAME];
  event.waitUntil(
    caches.keys().then((cacheNames) => {
      return Promise.all(
        cacheNames.map((cacheName) => {
          if (cacheWhitelist.indexOf(cacheName) === -1) {
            return caches.delete(cacheName);
          }
        })
      );
    })
  );
});
```

在这个示例中，我们定义了一个缓存名称和需要缓存的文件列表。在 `install` 事件中，我们打开指定的缓存并添加了需要的文件。在 `activate` 事件中，我们移除了不在白名单中的所有旧缓存。这样，当 Service Worker 文件更新后，新的缓存策略就会生效，旧的文件被更新。

**No cache scenario (No Service worker):** Your PWA app will be cached only when you use Service worker. Manifest.json will help adding your web app to home screen with a icon and open without address bar. If you don't have a service worker or if your browser don't support it, web page will be loaded fresh every single time. No Cache.

**Cache-On Scenario (With Service worker):** Assuming you have service workers configured, service workers can cache by lazy loading or prefetching the files that are configured for caching (You can include or exclude caching anything from html, CSS, images to JSON/XML API responses).

After the initial cache, service worker will use the cache to serve your apps network request based on [cache approach](https://developers.google.com/web/ilt/pwa/caching-files-with-service-worker) you have implemented from below ones.

*   cache falling back to network
*   Network falling back to cache
*   Cache then network

Most apps choose to [precache](https://github.com/GoogleChromeLabs/sw-precache) due to performance benefits and look for new files on loading, if any changes found will be loaded on next session or prompt user to refresh. With this solution, each file will have a long Hash string for each file cached by service worker. On load of each application, hash code from server will be fetched to match and find what file needs to be updated and the same will be updated in a separate service worker thread. You can notice this in network tab -> service worker response in chrome developer tools.

If you choose network-first approach, you can avoid showing old content on initial load, but loose significant performance benefits that comes with caching.

Only two events…
================

In essence, there are **only two events** that will automatically trigger a PWA update:

1.  A change in the linked `manifest.json`; e.g. a changed icon file or a changed `scope` or `start_url`.
2.  A one-character change in the controlling `service-worker.js`. Hence, if you store the version number in a `const` in this file and change it, an update of the PWA will be triggered.

When a change is detected, the new version will normally be activated only with the next PWA load. So, in all, **two reloads** are necessary to see a change.

How the update eventually is handled, is ultimately determined by the `service-worker.js`. Different update strategies may be defined in terms of the size and volatility of the PWA assets. It is also possible to activate a new service immediately.

However, there is one **important caveat.** Make sure that the **browser cache expiry directive** set by the `.htaccess` file of your asset server is set to a really short duration (e.g. `hours`) or even to [**none**](https://stackoverflow.com/a/66756683/2192488). Failing to do so, will result in the browser not seeing any change for days to come in the `manifest.json` nor the `service-worker.js`.

More details about service worker behaviour are available from [Google Web Fundamentals](https://developers.google.com/web/fundamentals/primers/service-workers/lifecycle).

When and how does a pwa update itself

清除Service Worker的缓存通常涉及以下几个步骤：

1. **注销Service Worker**：
   - 打开浏览器的开发者工具。
   - 转到“Application”面板。
   - 在左侧边栏中找到“Service Workers”。
   - 点击“Unregister”以注销当前域名下的Service Worker。

2. **清除缓存**：
   - 在相同的“Application”面板中，找到“Cache Storage”。
   - 展开“Cache Storage”部分，列出所有的缓存。
   - 右键点击需要删除的缓存，选择“Delete”来清除缓存。

3. **使用代码清除缓存**：
   可以在Service Worker的脚本中编写代码来清除缓存。例如：

   ```javascript
   self.addEventListener('activate', event => {
     event.waitUntil(
       caches.keys().then(cacheNames => {
         return Promise.all(
           cacheNames.map(cacheName => {
             // 假设'v1'是你想要保留的缓存的版本
             if (cacheName !== 'v1') {
               console.log('Service Worker: 清除旧缓存', cacheName);
               return caches.delete(cacheName);
             }
           })
         );
       })
     );
   });
   ```

   上述代码会在Service Worker激活时运行，它会遍历所有的缓存，并删除那些版本不是`'v1'`的缓存。

除了这些步骤，重要的是确保在更新Service Worker脚本后，让用户的浏览器获取到最新的Service Worker文件。通常，这可以通过更改Service Worker文件的内容来实现，因为浏览器会检查文件内容是否有变化来决定是否需要安装新的Service Worker。

例如，如果我刚完成一个项目，需要更新Service Worker以及对应的缓存，我会更新Service Worker脚本，可能是修改内部的缓存策略或者版本标签，然后将修改后的脚本部署到服务器。这样用户下次访问时，浏览器会检测到Service Worker脚本的内容更新，触发安装新的Service Worker，并在activate事件中清除旧的缓存。

总的来说，清除Service Worker的缓存需要综合运用开发者工具和编写Service Worker代码的方式来实现。这对于保持应用的性能和确保用户获得最新内容非常重要。

If you know the cache name you can simply call [`caches.delete()`](https://developer.mozilla.org/en-US/docs/Web/API/CacheStorage/delete) from anywhere you like in the worker:

    caches.delete(/*name*/);
    

And if you wanted to wipe all caches (and not wait for them, say this is a background task) you only need to [add this](https://developer.mozilla.org/en-US/docs/Web/API/CacheStorage/keys):

    caches.keys().then(function(names) {
        for (let name of names)
            caches.delete(name);
    });

Use this to delete outdated caches:

    self.addEventListener('activate', function(event) {
      event.waitUntil(
        caches.keys().then(function(cacheNames) {
          return Promise.all(
            cacheNames.filter(function(cacheName) {
              // Return true if you want to remove this cache,
              // but remember that caches are shared across
              // the whole origin
            }).map(function(cacheName) {
              return caches.delete(cacheName);
            })
          );
        })
      );
    });

Typically you update the `CACHE_NAME` in your service workers JS file so your worker installs again:

    self.addEventListener('install', evt => {
      evt.waitUntil(
        caches.open(CACHE_NAME).then(cache => cache.addAll(inputs))
      )
    })
    

Alternatively, to _clear_ the cache for a PWA find the cache name:

    self.caches.keys().then(keys => { keys.forEach(key => console.log(key)) })
    

then run the following to delete it:

    self.caches.delete('my-site-cache')
    

Then refresh the page.

If you see any worker-related errors in the console after refreshing, you may also need to unregister the registered workers:

    navigator.serviceWorker.getRegistrations()
      .then(registrations => {
        registrations.forEach(registration => {
          registration.unregister()
        }) 
      })

The most elegant solution, with async/await:

    const cacheName = 'v2';
    
    self.addEventListener('activate', event => {
    // Remove old caches
      event.waitUntil(
        (async () => {
          const keys = await caches.keys();
          return keys.map(async (cache) => {
            if(cache !== cacheName) {
              console.log('Service Worker: Removing old cache: '+cache);
              return await caches.delete(cache);
            }
          })
        })()
      )
    })

This is the only code that worked for me. It is my adaptation of [Mozilla documentation](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API/Using_Service_Workers#Deleting_old_caches) :

    //Delete all caches and keep only one
    const cachNameToKeep = 'myCache';
    
    //Deletion should only occur at the activate event
    self.addEventListener('activate', event => {
        var cacheKeeplist = [cacheName];
        event.waitUntil(
            caches.keys().then( keyList => {
                return Promise.all(keyList.map( key => {
                    if (cacheKeeplist.indexOf(key) === -1) {
                        return caches.delete(key);
                    }
                }));
            })
    .then(self.clients.claim())); //this line is important in some contexts
    });

How to clear cache of service worker?

当您想要卸载 Service Worker 时，可以通过几个步骤来实现：

1. **开发者工具中卸载：**

   如果是在开发过程中，可以直接通过浏览器的开发者工具来卸载 Service Worker。以下以 Google Chrome 浏览器为例：

   - 打开需要卸载 Service Worker 的网站。
   - 按 `F12` 或者右键选择“检查”打开开发者工具。
   - 切换到“Application”标签页。
   - 在左侧边栏的“Service Workers”选项下，可以看到当前激活的 Service Worker。
   - 有一个 "Unregister" 的按钮，点击它可以卸载当前的 Service Worker。

2. **编程卸载：**

   如果您希望在网站上编程实现卸载 Service Worker，可以通过以下代码实现：

   ```javascript
   if ('serviceWorker' in navigator) {
     navigator.serviceWorker.getRegistrations().then(function(registrations) {
       for (let registration of registrations) {
         registration.unregister();
       }
     }).catch(function(error) {
       console.log('Service Worker 注销失败: ', error);
     });
   }
   ```

   上面的代码段会找到所有注册的 Service Worker，并逐个注销它们。

3. **清除浏览器数据：**

   另一种卸载 Service Worker 的方法是清除网站的浏览器数据，包括缓存和本地存储。

   - 在 Chrome 浏览器中，可以按 `Ctrl+Shift+Delete` 快捷键打开“清除浏览数据”对话框。
   - 选择“高级”选项卡，勾选“Cookie 和其他站点数据”以及“缓存的图片和文件”。
   - 点击“清除数据”。

   这将删除所有的 Service Worker，以及相关的缓存和数据。

4. **手动修改Service Worker代码：**

   可以在 Service Worker 的代码中添加一个自毁逻辑，当满足特定条件时，自动卸载自身。例如：

   ```javascript
   self.addEventListener('install', (event) => {
     if (someCondition) {
       self.skipWaiting(); // 忽略等待，立即激活
     }
   });

   self.addEventListener('activate', (event) => {
     if (someCondition) {
       self.registration.unregister().then(() => {
         return self.clients.matchAll();
       }).then((clients) => {
         clients.forEach(client => client.navigate(client.url)); // 刷新页面
       });
     }
   });
   ```

   在上述代码中，`someCondition` 是一个占位符，表示某个您决定卸载 Service Worker 的条件。当条件满足时，Service Worker 将自我注销，并刷新所有的客户端页面。

通过这些方法，您可以有效地卸载 Service Worker。不过需要注意的是，卸载后相关的缓存功能将不再可用，如果是用户的设备上执行卸载操作，可能会影响到网站的离线功能和加载性能。因此，在执行卸载操作之前，请确保这是您所期望的。

### Removing Service Workers Programmatically:

You can remove service workers programmatically like this:

    navigator.serviceWorker.getRegistrations().then(registrations => {
        for (const registration of registrations) {
            registration.unregister();
        } 
    });
    

Docs: [getRegistrations](https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/getRegistrations), [unregister](https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerRegistration/unregister)

### Removing Service Workers Through The User Interface

You can also remove service workers under the Application tab in Chrome Devtools.

You can also go to the URL: **chrome://serviceworker-internals/** and unregister a serviceworker from there.

You can do this through **Chrome Developer Tool** as well as **Programatically**.

1.  Find all running instance or service worker by typing
    
    > **chrome://serviceworker-internals/**
    
    in a new tab and then select the serviceworker you want to unregister.
    
2.  Open Developer Tools (F12) and Select Application. Then Either
    
    > **Select Clear Storage -> Unregister service worker**
    
    or
    
    > **Select Service Workers -> Choose Update on Reload**
    
3.  Programatically
    

    if(window.navigator && navigator.serviceWorker) {
      navigator.serviceWorker.getRegistrations()
      .then(function(registrations) {
        for(let registration of registrations) {
          registration.unregister();
        }
      });
    }

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Expand snippet

In Google Chrome, you can go to **Developer tools (F12) -> Application -> Service worker** and **unregister** the service workers from the list for that specific domain.

[![Screenshot](https://i.stack.imgur.com/RtV2C.png)](https://i.stack.imgur.com/RtV2C.png)

This method is effective in development mode of a site and mostly they run on `localhost` which is you may need for other project's development.

FYI, in case you are using MacOS **Safari** browser, there is one way to forcibly unregister a service worker (steps and images for Safari 12.1):

1.  Safari > Preferences... > Privacy > Manage Website Data… [![Safari Preferences : Privacy](https://i.stack.imgur.com/yiEbw.png)](https://i.stack.imgur.com/yiEbw.png)
    
2.  Enter domain name (ex. 'localhost'), click "Remove" [![Safari Preferences : Privacy : manage website data](https://i.stack.imgur.com/am2s2.png)](https://i.stack.imgur.com/am2s2.png)
    

**Note:** In addition to service workers, this also will erase all caches, cookies, and databases for this domain.

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