Kode Injector от Maxim Topciu

Kode Injector injects your own JavaScript and CSS from local files into the websites you choose.

Map a local file to a hostname once. Every time you open a matching page, the extension applies that code automatically — on every reload, with no manual steps. Edit the file in your own editor and reload the page to see the change.

Built for web developers, QA testers, and designers who need to override or add code on pages they do not control.

Features

• Injection rules that map a site hostname to a local JavaScript file and a local CSS file
• Injection at document start, so styles apply before the page paints
• Toggle individual rules on and off, or delete them, from the options page
• A per-site switch in the toolbar popup that disables all injections for the current site
• A global pause that suspends every injection at once, and resumes with one click
• Light and dark themes
• Interface localized into 30 languages, with a language selector on the options page

Reading local files in Firefox

Firefox extension pages cannot read file:/// URLs, so Kode Injector reads your files through Kode Injector Helper — a small, open source, read-only companion application that you install separately. It reads only the files you configure in the extension. It installs no daemon, no login item, and no automatic updater, and it can uninstall itself from its own window.

The options page links to the right package for your operating system, or you can download it from GitHub Releases.

Privacy

Kode Injector collects no data. Your rules and your files stay on your computer.

Source code and issue tracker: https://github.com/maximtop/kode-injector