tabCapture

This permission is ideal for extensions that need to record, stream, or analyze the content of a single browser tab.

Examples:

• A "tab recording" extension.
• An extension that streams the content of a tab to a service like Twitch.
• A tool that takes high-quality video captures of web animations.
• A remote collaboration tool that shares a specific tab with other users.

{
  "name": "My Tab Recorder",
  "version": "1.0",
  "manifest_version": 3,
  "permissions": [
    "tabCapture"
  ]
}

Why is it risky?

This permission allows an extension to record the video and audio from a specific browser tab. This could be used to capture sensitive information inside that tab, like a video conference, a private document, or a movie you are watching.

The main safety feature is that Chrome will display a prominent visual indicator (like a red dot or a blue border) on any tab that is being recorded. This makes it hard for an extension to spy on you secretly. However, you should still be aware that anything you do in a tab being captured is visible to the extension.

This example starts capturing the active tab when the user clicks the extension icon.

// background.js

chrome.action.onClicked.addListener((tab) => {
  chrome.tabCapture.getMediaStreamId({ consumerTabId: tab.id }, (streamId) => {
    if (chrome.runtime.lastError) {
      console.error(chrome.runtime.lastError.message);
      return;
    }

    console.log("Got stream ID:", streamId);

    // In a real application, you would pass this streamId to a
    // content script or offscreen document to start the
    // navigator.mediaDevices.getUserMedia flow.
  });
});

// Example of how the streamId would be used inside an offscreen document
// (service workers don't have access to navigator.mediaDevices, so the
// stream must be consumed in a DOM context — typically an offscreen
// document declared with reasons: ['USER_MEDIA'] or 'DISPLAY_MEDIA').
/*
async function startCapture(streamId) {
  const stream = await navigator.mediaDevices.getUserMedia({
    audio: false,
    video: {
      mandatory: {
        chromeMediaSource: 'tab',
        chromeMediaSourceId: streamId
      }
    }
  });

  // Now 'stream' is a MediaStream of the tab's content.
  const video = document.createElement('video');
  video.srcObject = stream;
  video.play();
}
*/