index.md

---

title: userScripts.register()
slug: Mozilla/Add-ons/WebExtensions/API/userScripts/register
page-type: webextension-api-function
tags:
  - Add-ons
  - Extensions
  - Method
  - User Scripts API
  - WebExtensions
  - register
  - userScripts
browser-compat: webextensions.api.userScripts.register

---

{{AddonSidebar}}

This method enables user scripts to be registered from an extension's pages (such as the background page).

This method is very similar to the {{WebExtAPIRef("contentScripts.register","contentScripts.register()")}} API method (for example, they both return a promise that resolves to an API object with an {{WebExtAPIRef("userScripts.RegisteredUserScript.unregister","unregister()")}} method for unregistering the script). There are, however, differences in the options supported.

This is an asynchronous method that returns a {{JSxRef("Promise")}}.

Syntax

const registeredUserScript = await browser.userScripts.register(
  userScriptOptions       // object
);
// …
await registeredUserScript.unregister();

Parameters

• userScriptOptions

  • : object. Represents the user scripts to register. It has similar syntax to {{WebExtAPIRef("contentScripts.register","contentScripts.register()")}}.

    The UserScriptOptions object has the following properties:

    • scriptMetadata {{Optional_Inline}}

      • : A JSON object containing arbitrary metadata properties associated with the registered user scripts. However, while arbitrary, the object must be serializable, so it is compatible with the structured clone algorithm. This metadata is used to pass details from the script to the API script. For example, providing details of a subset of the APIs that need to be injected by the API script. The API does not use this metadata,

    • allFrames {{Optional_Inline}}

      • : Same as all_frames in the content_scripts key.

    • cookieStoreId {{optional_inline}}

      • : An array of cookie store ID strings or a string containing a cookie store ID. Registers the user script in the tabs that belong to the cookie store IDs. This enables scripts to be registered for all default or non-contextual identity tabs, private browsing tabs (if the extension is enabled in private browsing), the tabs of a contextual identity, or a combination of these.

    • excludeGlobs {{Optional_Inline}}

      • : Same as exclude_globs in the content_scripts key.

    • excludeMatches {{Optional_Inline}}

      • : Same as exclude_matches in the content_scripts key.

    • includeGlobs {{Optional_Inline}}

      • : Same as include_globs in the content_scripts key.

    • js

      • : An array of objects. Each object has either a property named file, which is a URL starting at the extension's manifest.json and pointing to a JavaScript file to register, or a property named code, which contains JavaScript code to register.

    • matchAboutBlank {{Optional_Inline}}

      • : Same as match_about_blank in the content_scripts key.

    • matches

      • : Same as matches in the content_scripts key. The URL patterns provided in matches must be enabled by the host permissions defined in the manifest permission property or enabled by the user from the optional_permissions list. For example, if matches includes https://mozilla.org/a a script is only registered if host permissions include, for example, https://mozilla.org/*. If the URL pattern isn't enabled, the call to register fails with the error "Permission denied to register a user script for ORIGIN".

    • runAt {{Optional_Inline}}

      • : Same as run_at in the content_scripts key.

Unlike content script options, the userScriptOptions object does not have a CSS property. Use {{WebExtAPIRef("contentScripts.register","contentScripts.register()")}} to dynamically register and unregister stylesheets.

Return value

A {{JSxRef("Promise")}} that is fulfilled with a {{WebExtAPIRef("userScripts.RegisteredUserScript","RegisteredUserScript")}} object that is use to unregister the user scripts.

Note: User scripts are unregistered when the related extension page (from which the user scripts were registered) is unloaded, so you should register user scripts from an extension page that persists at least as long as you want the user scripts to stay registered.

Browser compatibility

{{Compat}}

See also

• {{WebExtAPIRef("contentScripts.register","contentScripts.register()")}}

• {{WebExtAPIRef("userScripts.RegisteredUserScript.unregister","RegisteredUserScript.unregister()")}}