Every link picks its own browser.
Make LinkRouter your default browser and it stops being one. It sits in the menu bar, catches every link you click, checks it against your rules, and hands it to the right app. YouTube to Brave, work to Chrome, everything else to Safari. You never see it work.
A rule is a domain and a browser.
That's the whole model. Match a host against your list, top to bottom; the first rule that fits wins. Anything that matches nothing falls through to the default. Subdomains are opt-in per rule, so music.youtube.com rides the same rule as youtube.com if you want it to.
LinkRouter's shipped defaults. Add, edit, or clear them in Settings.
Two ways a link reaches it.
A link clicked inside Safari never leaves Safari to get re-handled, so the menu-bar app can't catch it. LinkRouter solves both paths at once.
The default-browser trick.
Set LinkRouter as your default browser and macOS sends it every http and https link from Mail, Slack, Notes, anywhere. It reads the host, finds the rule, and reopens the URL in the chosen browser. It never renders a page itself.
A Safari extension.
A bundled Web Extension watches navigations inside Safari and asks the same rule set. When a host matches a non-Safari rule, it hands the URL off through native messaging so the right browser opens. Same rules, both doors.
How it's built.
The native app registers as a URL handler at launch and listens for Apple Events, so a link arrives as a kAEGetURL event before anything is drawn. It opens the target with NSWorkspace and falls back to the system default if a browser isn't installed. Rules live in a shared App Group (group.zizzadoro.LinkRouter), which is how the menu-bar app and the Safari extension read the exact same list. There's no window unless you open Settings, no account, nothing leaves the Mac.
The menu-bar icon is a single SF Symbol: arrow.triangle.branch. A fork in the road, which is the whole app in one glyph.