JustZix is a free Chrome extension that injects custom CSS and JavaScript into any page using URL-pattern rules. It adds in-tab developer windows — a CSS pane, a JS pane, a JS Console (REPL) and a 6-tab Output Console (console logs, network requests, errors and the GTM dataLayer) — so you can edit, debug and customize sites without DevTools. Hide banners, force dark mode, QA a GTM setup, mark DEV/STAGING environments, or build small page tweaks that persist. No account required, no telemetry.
