CSS Mage > Inject Custom Styles Into Any Website, iFrames, Import/Export

Advanced custom CSS injector with persistent on-page UI.

CSS Mage is a powerful, persistent on-page CSS injector built for developers, designers, and power users. Instead of forcing you into a cramped browser popup, it provides a draggable, resizable, and encapsulated (Shadow DOM) editor that stays on the page while you work. It is designed to be a frictionless, pixel-perfect environment for theming, debugging, or overriding web styles. Key Features: • Live On-Page Editor: A floating, opacity-adjustable UI that lets you see your changes instantly without obstructing your view. • Dual Scoping: Seamlessly toggle between writing CSS strictly for the current domain or injecting global rules across all websites. • No Restrictions: Injects into iframes, shadow DOMs, and handles CORS restrictions. • True Editor Mechanics: Features reliable syntax highlighting, intelligent auto-formatting, robust undo/redo history, and standard keybindings (like Ctrl+/ for comments). • Legendary Themes: 13 built-in syntax themes, including Dark+, Dracula, Monokai, Nord, SynthWave '84, and GitHub Light/Dark. • Complete Portability: Export/import individual .css files, or backup and restore your entire library of site modifications via JSON. • Workflow Shortcuts: Open the editor with Ctrl+Shift+Space, single-click the extension icon to toggle the UI, or double-click the icon to instantly kill/enable all injected CSS as a quick sanity check.