manifest.json

[!NOTE] This article describes manifest.json for web extensions. If you are looking for information about the manifest.json in PWAs, check out the Web App Manifest article.

The manifest.json file is the only file that every extension using WebExtension APIs must contain.

Using manifest.json, you specify basic metadata about your extension such as the name and version, and can also specify aspects of your extension's functionality (such as background scripts, content scripts, and browser actions).

It is a JSON-formatted file, with one exception: it is allowed to contain //-style comments.

List of manifest.json keys

These are the manifest.json keys; these keys are available in Manifest V2 and above unless otherwise noted:

• action (Manifest V3 and above)
• author
• background
• browser_action (Manifest V2 only)
• browser_specific_settings
• chrome_settings_overrides
• chrome_url_overrides
• commands
• content_scripts
• content_security_policy
• declarative_net_request
• default_locale
• description
• developer
• devtools_page
• dictionaries
• externally_connectable (Not supported in Firefox)
• homepage_url
• host_permissions (Manifest V3 and above)
• icons
• incognito
• manifest_version
• name
• offline_enabled (Not supported in Firefox)
• omnibox
• optional_host_permissions (Manifest V3 and above)
• optional_permissions
• options_page
• options_ui
• page_action (Manifest V2 only in Chrome)
• permissions
• protocol_handlers (Firefox only)
• short_name
• sidebar_action
• storage (Not supported in Firefox)
• theme
• theme_experiment (Firefox only) (experimental)
• user_scripts (Manifest V2 only)
• version
• version_name
• web_accessible_resources

Notes about manifest.json keys

• "manifest_version", "version", and "name" are the only mandatory keys.
• "default_locale" must be present if the _locales directory is present, and must be absent otherwise.
• "browser_specific_settings" is not supported in Google Chrome.

Accessing manifest.json keys at runtime

You can access your extension's manifest from the extension's JavaScript using the {{WebExtAPIRef("runtime.getManifest()")}} function:

browser.runtime.getManifest().version;

Example

The block below shows the basic syntax for some common manifest keys.

[!NOTE] This is not intended to be used as a copy-paste-ready example. Selecting the keys you'll need depends on the extension you are developing.

For complete example extensions, see Example extensions.

{
  "browser_specific_settings": {
    "gecko": {
      "id": "@addon-example",
      "strict_min_version": "42.0"
    }
  },

  "background": {
    "scripts": ["jquery.js", "my-background.js"]
  },

  "browser_action": {
    "default_icon": {
      "19": "button/geo-19.png",
      "38": "button/geo-38.png"
    },
    "default_title": "Whereami?",
    "default_popup": "popup/geo.html"
  },

  "commands": {
    "toggle-feature": {
      "suggested_key": {
        "default": "Ctrl+Shift+Y",
        "linux": "Ctrl+Shift+U"
      },
      "description": "Send a 'toggle-feature' event"
    }
  },

  "content_security_policy": "script-src 'self' https://example.com; object-src 'self'",

  "content_scripts": [
    {
      "exclude_matches": ["*://developer.mozilla.org/*"],
      "matches": ["*://*.mozilla.org/*"],
      "js": ["borderify.js"]
    }
  ],

  "default_locale": "en",

  "description": "…",

  "icons": {
    "48": "icon.png",
    "96": "[email protected]"
  },

  "manifest_version": 2,

  "name": "…",

  "page_action": {
    "default_icon": {
      "19": "button/geo-19.png",
      "38": "button/geo-38.png"
    },
    "default_title": "Whereami?",
    "default_popup": "popup/geo.html"
  },

  "permissions": ["webNavigation"],

  "version": "0.1",

  "user_scripts": {
    "api_script": "apiscript.js"
  },

  "web_accessible_resources": ["images/my-image.png"]
}

Browser compatibility

{{Compat}}

See also

{{WebExtAPIRef("permissions")}} JavaScript API