chrome.userScripts

Description

Use the userScripts API to execute user scripts in the User Scripts context.

Permissions

userScripts

To use the chrome.userScripts API, add the "userScripts" permission to your manifest.json and "host_permissions" for sites you want to run scripts on.

{
  "name": "User script test extension",
  "manifest_version": 3,
  "minimum_chrome_version": "120",
  "permissions": [
    "userScripts"
  ],
  "host_permissions": [
    "*://example.com/*"
  ]
}

Availability

Chrome 120+ MV3+

Concepts and usage

A user script is a bit of code injected into a web page to modify its appearance or behavior. Scripts are either created by users or downloaded from a script repository or a user script extension.

Developer mode for extension users

As an extension developer, you already have Developer mode enabled in your installation of Chrome. For user script extensions, your users will also need to enable developer mode. Here are instructions that you can copy and paste into your own documentation.

  1. Go to the Extensions page by entering chrome://extensions in a new tab. (By design chrome:// URLs are not linkable.)
  2. Enable Developer Mode by clicking the toggle switch next to Developer mode.

    Extensions page

    Extensions page (chrome://extensions)

You can determine if developer mode is enabled by checking whether chrome.userScripts throws an error. For example:

function isUserScriptsAvailable() {
  try {
    // Property access which throws if developer mode is not enabled.
    chrome.userScripts;
    return true;
  } catch {
    // Not available.
    return false;
  }
}

Work in isolated worlds

Both user and content scripts can run in an isolated world or in the main world. An isolated world is an execution environment that isn't accessible to a host page or other extensions. This lets a user script change its JavaScript environment without affecting the host page or other extensions' user and content scripts. Conversely, user scripts (and content scripts) are not visible to the host page or the user and content scripts of other extensions. Scripts running in the main world are accessible to host pages and other extensions and are visible to host pages and to other extensions. To select the world, pass "USER_SCRIPT" or "MAIN" when calling userScripts.register().

To configure a content security policy for the USER_SCRIPT world, call userScripts.configureWorld():

chrome.userScripts.configureWorld({
  csp: "script-src 'self'"
});

Messaging

Like content scripts and offscreen documents, user scripts can communicate with other parts of an extension using messaging. Unlike other types of messages, user script messages use their own methods: runtime.onUserScriptMessage and chrome.runtime.onUserScriptConnect events.

Before sending a message, you must call configureWorld() with the messaging argument set to true. Note that both the csp and messaging arguments can be passed at the same time.

chrome.userScripts.configureWorld({
  messaging: true
});

Extension updates

User scripts are cleared when an extension updates. You can add them back running code via the runtime.onInstalled event handler in the extension service worker. Respond only to the "update" reason passed to the event callback.

Example

The example below is from the userScript sample in our samples repo.

Register a script

The following example shows a basic call to register(). The first argument is an array of objects defining the scripts to be registered. There are more options than are shown here.

chrome.userScripts.register([{
  id: 'test',
  matches: ['*://*/*'],
  js: [{code: 'alert("Hi!")'}]
}]);

Types

ExecutionWorld

The JavaScript world for a user script to execute within.

Enum

"MAIN"
Specifies the execution environment of the DOM, which is the execution environment shared with the host page's JavaScript.

"USER_SCRIPT"
Specifies the execution environment that is specific to user scripts and is exempt from the page's CSP.

RegisteredUserScript

Properties

  • allFrames

    boolean optional

    If true, it will inject into all frames, even if the frame is not the top-most frame in the tab. Each frame is checked independently for URL requirements; it will not inject into child frames if the URL requirements are not met. Defaults to false, meaning that only the top frame is matched.

  • excludeGlobs

    string[] optional

    Specifies wildcard patterns for pages this user script will NOT be injected into.

  • excludeMatches

    string[] optional

    Excludes pages that this user script would otherwise be injected into. See Match Patterns for more details on the syntax of these strings.

  • id

    string

    The ID of the user script specified in the API call. This property must not start with a '_' as it's reserved as a prefix for generated script IDs.

  • includeGlobs

    string[] optional

    Specifies wildcard patterns for pages this user script will be injected into.

  • The list of ScriptSource objects defining sources of scripts to be injected into matching pages.

  • matches

    string[] optional

    Specifies which pages this user script will be injected into. See Match Patterns for more details on the syntax of these strings. This property must be specified for ${ref:register}.

  • runAt

    RunAt optional

    Specifies when JavaScript files are injected into the web page. The preferred and default value is document_idle.

  • world

    ExecutionWorld optional

    The JavaScript execution environment to run the script in. The default is `USER_SCRIPT`.

ScriptSource

Properties

  • code

    string optional

    A string containing the JavaScript code to inject. Exactly one of file or code must be specified.

  • file

    string optional

    The path of the JavaScript file to inject relative to the extension's root directory. Exactly one of file or code must be specified.

UserScriptFilter

Properties

  • ids

    string[] optional

    getScripts only returns scripts with the IDs specified in this list.

WorldProperties

Properties

  • csp

    string optional

    Specifies the world csp. The default is the `ISOLATED` world csp.

  • messaging

    boolean optional

    Specifies whether messaging APIs are exposed. The default is false.

Methods

configureWorld()

Promise
chrome.userScripts.configureWorld(
  properties: WorldProperties,
  callback?: function,
)

Configures the `USER_SCRIPT` execution environment.

Parameters

  • properties

    Contains the user script world configuration.

  • callback

    function optional

    The callback parameter looks like:

    ()=>void

Returns

  • Promise<void>

    Promises are supported in Manifest V3 and later, but callbacks are provided for backward compatibility. You cannot use both on the same function call. The promise resolves with the same type that is passed to the callback.

getScripts()

Promise
chrome.userScripts.getScripts(
  filter?: UserScriptFilter,
  callback?: function,
)

Returns all dynamically-registered user scripts for this extension.

Parameters

Returns

  • Promises are supported in Manifest V3 and later, but callbacks are provided for backward compatibility. You cannot use both on the same function call. The promise resolves with the same type that is passed to the callback.

register()

Promise
chrome.userScripts.register(
  scripts: RegisteredUserScript[],
  callback?: function,
)

Registers one or more user scripts for this extension.

Parameters

  • Contains a list of user scripts to be registered.

  • callback

    function optional

    The callback parameter looks like:

    ()=>void

Returns

  • Promise<void>

    Promises are supported in Manifest V3 and later, but callbacks are provided for backward compatibility. You cannot use both on the same function call. The promise resolves with the same type that is passed to the callback.

unregister()

Promise
chrome.userScripts.unregister(
  filter?: UserScriptFilter,
  callback?: function,
)

Unregisters all dynamically-registered user scripts for this extension.

Parameters

  • filter

    If specified, this method unregisters only the user scripts that match it.

  • callback

    function optional

    The callback parameter looks like:

    ()=>void

Returns

  • Promise<void>

    Promises are supported in Manifest V3 and later, but callbacks are provided for backward compatibility. You cannot use both on the same function call. The promise resolves with the same type that is passed to the callback.

update()

Promise
chrome.userScripts.update(
  scripts: RegisteredUserScript[],
  callback?: function,
)

Updates one or more user scripts for this extension.

Parameters

  • Contains a list of user scripts to be updated. A property is only updated for the existing script if it is specified in this object. If there are errors during script parsing/file validation, or if the IDs specified do not correspond to a fully registered script, then no scripts are updated.

  • callback

    function optional

    The callback parameter looks like:

    ()=>void

Returns

  • Promise<void>

    Promises are supported in Manifest V3 and later, but callbacks are provided for backward compatibility. You cannot use both on the same function call. The promise resolves with the same type that is passed to the callback.