Overview
Inject CSS per URL
Site CSS is a minimal extension to apply custom user CSS to sites and pages you visit. Add a URL pattern (matching every page, a host, a specific page, or anything in between), paste in some CSS, and it applies every time you visit. Site CSS does the Right Thing whenever possible: - Extremely minimal, auditable implementation (no dependencies, build steps, or built-in autoformatters here) - Styles sync via your browser profile and update live as you edit - Styles apply before document load with no flash of unstyled content - Styles are injected as user-origin CSS as in the halcyon days of `userContent.css`: Site CSS rules < page rules < page `!important` rules < Site CSS `!important` rules - Efficient filter implementation so pages without custom styles don't slow down - Works in iframes and on file:// urls - No account, no tracking, no data collection - Open source and public domain (CC0): https://github.com/twilligon/site-css
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Details
- Version1.1
- UpdatedAugust 24, 2026
- Size13.37KiB
- Languages5 languages
- DeveloperWebsite
Email
extensions@twilligon.com - Non-traderThis developer has not identified itself as a trader. For consumers in the European Union, please note that consumer rights do not apply to contracts between you and this developer.
Privacy
This developer declares that your data is
- Not being sold to third parties, outside of the approved use cases
- Not being used or transferred for purposes that are unrelated to the item's core functionality
- Not being used or transferred to determine creditworthiness or for lending purposes
Support
For help with questions, suggestions, or problems, visit the developer's support site