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Chrome Manifest v2 background script vs v3 service worker

In Chrome’s Manifest V2 if you wanted to have a script that ran in the background of the Chrome browser you would register it in the background field with the scripts key in the manifest.js file:

{
  "manifest_version": 2,
  ...
  "background": {
    "scripts": ["background.js"]
  }
}

This changed in the release of Manifest V3 where now background scripts are to be registered in the background field with the service_worker key in the manifest.js file:

{
  "manifest_version": 3,
  ...
  "background": {
    "service_worker": "background.js"
  }
}

In both of implementations this script runs in a separate thread than the browser and can be used to make network requests, interact with data storage mechanisms, broadcast messages, etc. Service workers are non-blocking scripts, meaning they are completely asynchronous.

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