Every shortcut carries its own site scope. There are three modes.

Mode	Behaviour
All sites	The default. The shortcut works everywhere.
Only these sites	An allow list. The shortcut works on the listed hosts and nowhere else.
Except these sites	A deny list. The shortcut works everywhere but the listed hosts.

How a pattern matches

Patterns are matched against the page's hostname. One pattern per line.

Pattern	Matches	Does not match
example.com	example.com, www.example.com, a.b.example.com	notexample.com
*.example.com	Identical to the line above — the bare domain and its subdomains	notexample.com

A plain domain already includes its subdomains, so example.com and *.example.com behave the same way. The *. form exists because people expect to be able to write it; it is not a different rule. There is no pattern that matches a domain without its subdomains.

Paths, query strings and ports are not part of the match. A rule for github.com applies to every page on GitHub.

Write the bare hostname. You do not have to be careful about the shape of it: GitHub.com, https://github.com, github.com/user and github.com:3000 are all read as github.com when the rule is saved. One form is not guessed at, because two readings are possible: *github.com, a wildcard with no dot. The options page leaves that line alone and says so under the box — write *.github.com, or plain github.com, which already covers subdomains.

Worked examples

• Mute only where you watch video. Bind Alt+M to Mute / unmute tab, mode Only these sites, patterns youtube.com and twitch.tv. Both cover their subdomains automatically.
• Keep a shortcut away from an app that already uses it. Bind Alt+J to Next tab, mode Except these sites, pattern docs.google.com. It works everywhere else.
• Two different actions on the same keys. Nothing stops you binding the same combination twice with non-overlapping site scopes — the first matching rule in list order wins. New rules land at the end of the list, and each row has up and down buttons if you need a narrower rule to win over a broader one.

What happens on pages the extension cannot reach

Chrome does not allow extensions to run on its own internal pages (chrome:// addresses, the Web Store, and the new tab page in some configurations). Page-level shortcuts do not fire there. This is a browser rule, not a setting.