Can you access chrome:// pages from an extension?

When you're writing the manifest.json file, you have to specify matches for your content scripts. The http and https work fine, but if I try to include chrome://*/* or any variant of it, I get an error that I'm attempting to use an invalid scheme for my matches.

Is it not allowed?

By default you cannot run on a chrome:// url page.
However, there is an option in chrome://flags/#extensions-on-chrome-urls:

Extensions on chrome:// URLs (Mac, Windows, Linux, Chrome OS, Android)
Enables running extensions on chrome:// URLs, where extensions explicitly request this permission.

You still have to specify pages that your extension can run on and wildcards are not accepted - so you have to specify the full URL eg chrome://extensions/

Until Chrome 139 it also allowed access to chrome-extension:// URLs, now there's a separate flag, see below for more info.

Chrome 139 and newer

• The Extensions on chrome:// URLs flag is ignored by default since Chrome 139 in Google's stable/beta versions of the browser (other vendors may do the same).

  You can restore its functionality:

  • add the following to the command line of your browser's shortcut and restart it:
    --disable-features=DisableExtensionsOnChromeUrlsSwitch
  • use a separate Chrome installation from a test channel of the browser (Dev or Canary).

• A new Extensions on chrome-extension:// URLs flag is now required to allow access to chrome-extension:// URLs.