Code Injector & Web Editor

Add your own JavaScript and CSS to any website. Edit in the popup, the side panel, DevTools or a full-page editor.

Add your own JavaScript and CSS to any website. Hide what bothers you, restyle the sites you use every day, fix a broken page, or test a change before you ship it. Your code runs on every page load, only on the sites you choose. ★ WHAT YOU CAN DO • Add JavaScript and CSS to one site, a site and its subdomains, every site, or your own match patterns. • Load scripts and stylesheets by URL: a library from a CDN, or a build from your localhost dev server. • Hide any element with a click. Pick it on the page, then choose Hide or Style in editor. No code needed. • Watch your CSS change the page as you type. Run JavaScript right away with Run now (Ctrl+Enter). • Switch single snippets, or everything at once, on and off from the toolbar. ★ EDIT WHERE YOU WORK • Toolbar popup: see what runs on the current site, switch it on or off, add new code. • Side panel: the editor right beside the page. • DevTools panel: a Code Injector tab that lists only what runs on the page you're inspecting. • Full-page editor: all your snippets grouped by site, with search across names and code. ★ A REAL CODE EDITOR • Syntax highlighting, error checking, autocomplete and search. • Autosave, Format code, light and dark themes, adjustable font size. • Errors thrown by your scripts are caught and shown next to the code, with the line they came from. • Starter templates: hide elements, dark mode, auto-click, run on URL change and more. • Keyboard shortcuts to pause everything, open the editor or pick an element. ★ WORKS WHERE OTHERS DON'T • Runs on sites with a strict Content Security Policy, such as YouTube, GitHub and X, through the browser's User Scripts API. It never removes a site's security headers. • Choose when a script runs (page start, DOM ready or page idle) and whether it runs in the page or in an isolated world. • CSS works right after you install. JavaScript needs a one-time "Allow User Scripts" switch in Chrome; the setup page walks you through it. ★ SWITCH IN SECONDS • Import from User JavaScript and CSS files. • Export everything to a JSON file, and import it on another computer or in another browser. ★ PRIVATE BY DESIGN • No account, no ads, no tracking, no analytics. • Your code stays in your browser. Nothing you write is sent anywhere. • Code Injector only runs code that you wrote or added yourself. ★ UPGRADING FROM VERSION 0.9? Version 2 is rebuilt for Manifest V3. Your saved files are safe: each one moves into the new version automatically the first time you open its site, with the same IDs and the same $injectExtension page API. Turn on "Allow User Scripts" once, and they run just like before, now also on sites with strict security policies. ★ FOR DEVELOPERS • Data files (JSON, HTML, YAML, SQL and more) that your scripts read with $injectExtension.getResource(id). • Load a build from localhost on a live site to test a fix. • "Don't run on this site" exceptions for snippets that run on many sites.