script-o-matic

Run your own JavaScript automatically on domains you choose.

script-o-matic runs your own JavaScript on the websites you choose — automatically, on every page load, on the exact domains you pick. WHAT IT DOES • Write a rule: a name, a domain like example.com, and your JavaScript • The script runs automatically on that domain and all its subdomains, on every newly loaded page • Enable, disable, edit, or delete rules at any time from a clean options page • Light, dark, or automatic theme that follows your system appearance SIMPLE, PREDICTABLE MATCHING • Enter a bare domain or paste a full URL — it's reduced to its hostname • example.com matches both HTTP and HTTPS, every path, and subdomains such as www.example.com • The match scope is shown before you save, so there are no surprises PRIVATE BY DESIGN • Everything is stored locally in your browser — no account, no sync, no server • No telemetry, no analytics, no remote code download • Domain access is requested only when you save an enabled rule for that domain • Each rule runs in its own isolated world: it can access the page's DOM but not the page's JavaScript variables or other rules SAFE TO USE • Your code's syntax is checked locally before registration, so a typo never silently breaks a working rule • A safety disclaimer reminds you to only paste code you trust (dismissible) • Clear per-rule status: Registered, Needs access, or Registration error — with guidance to fix each GOOD TO KNOW • Requires Chrome 138 or newer with the "Allow User Scripts" toggle enabled in the extension's details • Scripts run once per newly loaded top-level page at document idle; single-page-app route changes don't retrigger them • Greasemonkey/Tampermonkey metadata and GM_* APIs are not supported — just plain JavaScript • Chrome-internal pages and the Chrome Web Store cannot run user scripts Free and open source under GPL-3.0.