content_scripts

Type Array
Mandatory No
Example 
"content_scripts": [
  {
    "matches": ["*://*.mozilla.org/*"],
    "js": ["borderify.js"]
  }
]

Instructs the browser to load content scripts into web pages whose URL matches a given pattern.

This key is an array. Each item is an object which:

  • must contain a key named matches, which specifies the URL patterns to be matched in order for the scripts to be loaded;
  • may contain keys named js and css, which list scripts and/or stylesheets to be loaded into matching pages; and
  • may contain a number of other properties that control finer aspects of how and when content scripts are loaded.

Details of all the keys you can include are given in the table below.

Name Type Description
all_frames Boolean
true
Inject the scripts specified in js and css into all frames matching the specified URL requirements, even if the frame is not the topmost frame in a tab. This does not inject into child frames where only their parent matches the URL requirements and the child frame does not match the URL requirements. The URL requirements are checked for each frame independently.

Note: This also applies to any tracker or ad that uses iframes, which means that enabling this could make your content script get called dozens of times on some pages.

false
Inject only into frames matching the URL requirements which are the topmost frame in a tab.

Defaults to false.
css Array

An array of paths, relative to manifest.json, referencing CSS files that will be injected into matching pages.

Files are injected in the order given, and at the time specified by run_at.

Note: Firefox resolves URLs in injected CSS files relative to the CSS file itself, rather than to the page it's injected into.
exclude_globs Array An array of strings containing wildcards. See Matching URL patterns below.
exclude_matches Array An array of match patterns. See Matching URL patterns below.
include_globs Array An array of strings containing wildcards. See Matching URL patterns below.
js Array

An array of paths, relative to manifest.json, referencing JavaScript files that will be injected into matching pages.

Files are injected in the order given. This means that, for example, if you include jQuery here followed by another content script, like this...

"js": ["jquery.js", "my-content-script.js"]

...then "my-content-script.js" can use jQuery.

The files are injected after any files in css, and at the time specified by run_at.
match_about_blank Boolean

Insert the content scripts into pages whose URL is "about:blank" or "about:srcdoc", if the URL of the page that opened or created this page matches the patterns specified in the rest of the content_scripts key.

This is especially useful to run scripts in empty iframes , whose URL is "about:blank". To do this you should also set the all_frames key.

For example, suppose you have a content_scripts key like this:

  "content_scripts": [
    {
      "js": ["my-script.js"],
      "matches": ["https://example.org/"],
      "match_about_blank": true,
      "all_frames": true
    }
  ]

If the user loads https://example.org/, and this page embeds an empty iframe, then "my-script.js" will be loaded into the iframe.

Note: match_about_blank is supported in Firefox from version 52.

Note that in Firefox, content scripts won't be injected into empty iframes at "document_start", even if you specify that value in run_at .
matches Array

An array of match patterns. See Matching URL patterns below.

This is the only mandatory key.
run_at String

This option determines when the files specified in css and js are injected. You can supply one of three strings here, each of which identifies a state in the process of loading a document. The states directly correspond to Document.readyState:

"document_start"
Corresponds to loading. The DOM is still loading.
"document_end"
Corresponds to interactive. The DOM has finished loading, but resources such as scripts and images may still be loading.
"document_idle"
Corresponds to complete. The document and all its resources have finished loading.

The default value is "document_idle".

In all cases, files in js are injected after files in css.

Matching URL patterns

The "content_scripts" key attaches content scripts to documents based on URL matching: if the document's URL matches the specification in the key, then the script will be attached. There are four properties inside "content_scripts" that you can use for this specification:

matches
an array of match patterns
exclude_matches
an array of match patterns
include_globs
an array of globs
exclude_globs
an array of globs

To match one of these properties, a URL must match at least one of the items in its array. For example, given a property like:

"matches": ["*://*.example.org/*", "*://*.example.com/*"]

Both http://example.org/ and http://example.com/ will match.

Since matches is the only mandatory key, the other three keys are used to limit further the URLs that match. To match the key as a whole, a URL must:

  • match the matches property
  • AND match the include_globs property, if present
  • AND NOT match the exclude_matches property, if present
  • AND NOT match the exclude_globs property, if present

globs

A glob is just a string that may contain wildcards.

There are two types of wildcard, and you can combine them in the same glob:

  1. * matches zero or more characters
  2. ? matches exactly one character.

For example: "*na?i" would match "illuminati" and "annunaki", but not "sagnarelli".

Example

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

This injects a single content script borderify.js into all pages under mozilla.org or any of its subdomains, whether served over HTTP or HTTPS.

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

This injects two content scripts into all pages under mozilla.org or any of its subdomains except developer.mozilla.org, whether served over HTTP or HTTPS.

The content scripts see the same view of the DOM and are injected in the order they appear in the array, so borderify.js can see global variables added by jquery.js.

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
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
?
?
?
all_frames
Yes
14
48
?
Yes
14
?
?
48
?
?
?
css
Yes
14
48
?
Yes
14
?
?
48
?
?
?
exclude_globs
Yes
14
48
?
Yes
No
?
?
48
?
?
?
exclude_matches
Yes
14
48
?
Yes
14
?
?
48
?
?
?
include_globs
Yes
14
48
?
Yes
No
?
?
48
?
?
?
js
Yes
14
48
?
Yes
14
?
?
48
?
?
?
match_about_blank
Yes
14
52
Content scripts won't be injected into empty iframes at 'document_start' even if you specify that value in 'run_at'.
?
Yes
No
?
?
52
Content scripts won't be injected into empty iframes at 'document_start' even if you specify that value in 'run_at'.
?
?
?
matches
Yes
14
48
?
Yes
14
?
?
48
?
?
?
run_at
Yes
14
48
?
Yes
14
Content scripts are not applied to tabs until the user grants permission via the extension's access popover in the toolbar. Additional loads after permission is granted will respect run_at.
?
?
48
?
?
?

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/content_scripts