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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

manifest.json keys are listed below:

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 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": "[email protected]",
      "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

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`author`	Yes	14 This key is mandatory in Microsoft Edge.	52	?	Yes	14 Not displayed in Safari Extensions preferences.	?	?	52	?	?	?
`background`	Yes	14	48	?	Yes	14	?	?	48	?	?	?
`browser_action`	Yes If an extension defines a browser action, it is not allowed to define a page action as well.	14	48	?	Yes If an extension defines a browser action, it is not allowed to define a page action as well.	14 If an extension defines a browser action, it is not allowed to define a page action as well.	?	?	55	?	?	?
`browser_specific_settings`	No	15-79	48 42 Mandatory before Firefox 48.	?	No	14 Supports `strict_min_version` and `strict_max_version` in a `safari` block.	?	?	48 42 Mandatory before Firefox 48.	?	?	?
`chrome_settings_overrides`	Yes	79	55	?	No	No	?	?	No	?	?	?
`chrome_url_overrides`	Yes	79	54	?	No	14.1	?	?	No	?	?	?
`commands`	Yes	79	48	?	Yes	14 Ability to change the keyboard shortcut for a command not supported.	?	?	No	?	?	?
`content_scripts`	Yes Content scripts are not applied to tabs already open when the extension is loaded.	14	48	?	Yes Content scripts are not applied to tabs already open when the extension is loaded.	14 Content scripts are not applied to tabs until the user grants permission via the extension's access popover in the toolbar.	?	?	48	?	?	?
`content_security_policy`	Yes	14 Only the default content security policy is supported: "script-src 'self'; object-src 'self';".	48 Firefox does not support 'http://127.0.0.1' or 'http://localhost' as script sources: they must be served over HTTPS.	?	Yes	14	?	?	No	?	?	?
`default_locale`	Yes	14	48	?	Yes	14	?	?	48	?	?	?
`description`	Yes	14	48	?	Yes	14	?	?	48	?	?	?
`developer`	No	No	52	?	Yes	No	?	?	52	?	?	?
`devtools_page`	Yes	79	54	?	Yes	No	?	?	No	?	?	?
`externally_connectable`	Yes	79	No See bug 1319168.	?	Yes	No	?	?	No	?	?	?
`homepage_url`	Yes	79	48	?	Yes	14 Not displayed in Safari Extensions preferences.	?	?	48	?	?	?
`icons`	Yes Chrome does not support SVG format for icons. It is recommended to use PNG images.	14	48	?	Yes	14 SVG icons are not supported.	?	?	48	?	?	?
`incognito`	Yes	≤18	48	?	Yes	No	?	?	48	?	?	?
`manifest_version`	4	14	48	?	15	14	?	?	48	?	?	?
`name`	Yes	14	48	?	Yes	14	?	?	48	?	?	?
`offline_enabled`	Yes	79	No	?	Yes	No	?	?	No	?	?	?
`omnibox`	Yes	79	52	?	Yes	No	?	?	No	?	?	?
`optional_permissions`	Yes	79	55	?	Yes	14	?	?	55	?	?	?
`options_page`	Yes	14	No	?	15	14	?	?	No	?	?	?
`options_ui`	40	79	48	?	27	14	?	?	57	?	?	?
`page_action`	Yes If an extension defines a page action, it is not allowed to define a browser action as well. 49 Since Chrome 49, page actions are displayed on the toolbar, rather than in the address bar.	14	48	?	Yes If an extension defines a page action, it is not allowed to define a browser action as well.	14 If an extension defines a page action, it is not allowed to define a browser action as well.	?	?	Yes	?	?	?
`permissions`	Yes	14	48	?	Yes	14	?	?	48	?	?	?
`protocol_handlers`	No	No	54	?	No	No	?	?	54	?	?	?
`short_name`	Yes	14	48	?	Yes	14	?	?	48	?	?	?
`sidebar_action`	No	No	54	?	30	No	?	?	No	?	?	?
`storage`	Yes	79	No	?	No	14	?	?	No	?	?	?
`theme`	Yes	79	55	?	No	No	?	?	Yes	?	?	?
`theme_experiment`	No	No	63	?	No	No	?	?	No	?	?	?
`user_scripts`	Yes	79	68	?	No	No	?	?	68	?	?	?
`version`	Yes Valid Chrome versions are a subset of valid Firefox versions.	14	48	?	Yes	14	?	?	48	?	?	?
`version_name`	Yes	79	No	?	Yes	14	?	?	No	?	?	?
`web_accessible_resources`	Yes	14	48	?	Yes	14	?	?	48	?	?	?