Match patterns

Published on Tuesday, September 18, 2012 • Updated on Saturday, October 28, 2017

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Host permissions and content script matching are based on a set of URLs defined by match patterns. A match pattern is essentially a URL that begins with a permitted scheme (http, https, file, or ftp, and that can contain '*' characters. The special pattern <all_urls> matches any URL that starts with a permitted scheme. Each match pattern has 3 parts:

scheme — for example, http or file or *

Note: Access to file URLs isn't automatic. The user must visit the extensions management page and opt in to file access for each extension that requests it.
host — for example, www.google.com or *.google.com or *; if the scheme is file, there is no host part
path — for example, /*, /foo*, or /foo/bar. The path must be present in a host permission, but is always treated as /*.

Here's the basic syntax:

 := ://
 := '*' | 'http' | 'https' | 'file' | 'ftp'
 := '*' | '*.' +
 := '/'

The meaning of '*' depends on whether it's in the scheme, host, or path part. If the scheme is *, then it matches either http or https, and not file, or ftp. If the host is just *, then it matches any host. If the host is *._hostname_, then it matches the specified host or any of its subdomains. In the path section, each '*' matches 0 or more characters. The following table shows some valid patterns.

Pattern	What it does	Examples of matching URLs
`http:///`	Matches any URL that uses the `http` scheme	http://www.google.com/ http://example.org/foo/bar.html
`http:///foo`	Matches any URL that uses the `http` scheme, on any host, as long as the path starts with `/foo`	http://example.com/foo/bar.html http://www.google.com/foo
`https://.google.com/foobar`	Matches any URL that uses the `https` scheme, is on a google.com host (such as www.google.com, docs.google.com, or google.com), as long as the path starts with `/foo` and ends with `bar`	https://www.google.com/foo/baz/bar https://docs.google.com/foobar
`http://example.org/foo/bar.html`	Matches the specified URL	http://example.org/foo/bar.html
`file:///foo*`	Matches any local file whose path starts with `/foo`	file:///foo/bar.html file:///foo
`http://127.0.0.1/*`	Matches any URL that uses the `http` scheme and is on the host 127.0.0.1	http://127.0.0.1/ http://127.0.0.1/foo/bar.html
`://mail.google.com/`	Matches any URL that starts with `http://mail.google.com` or `https://mail.google.com`.	http://mail.google.com/foo/baz/bar https://mail.google.com/foobar
`<all_urls>`	Matches any URL that uses a permitted scheme. (See the beginning of this section for the list of permitted schemes.)	http://example.org/foo/bar.html file:///bar/baz.html

Here are some examples of invalid pattern matches:

Bad pattern	Why it's bad
`http://www.google.com`	No path
`http://*foo/bar`	'' in the host* can be followed only by a '.' or '/'
`http://foo.*.bar/baz`	If '' is in the host*, it must be the first character
`http:/bar`	Missing scheme separator ("/" should be "//")
`foo://*`	Invalid scheme

Some schemes are not supported in all contexts.