StyleInject – Custom CSS Injector

StyleInject lets you write custom CSS rules for any website and have them automatically injected on every visit. Create per-domain rules using simple glob patterns — example.com, *.example.com, or * for all pages. Changes apply live as you type, with a real-time preview before saving. Built-in CSS editor features syntax highlighting, line numbers, auto-formatting, and 12 ready-made snippets for common tasks like hiding cookie banners, widening reading columns, or applying dark mode. Rules can be toggled on/off individually or all at once. Export and import your rule library as JSON.