
FireCSS by derivia
Save custom CSS to webpages
3 Users3 Users
You'll need Firefox to use this extension
Extension Metadata
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About this extension
This Firefox extension lets you easily apply custom CSS to any webpage. Simply enter a URL (with wildcard support) and your CSS code, and the extension will inject the styles into the active tab. Perfect for customizing the appearance of websites or testing CSS in real-time.
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Permissions and dataLearn more
Required permissions:
- Access browser tabs
- Access your data for all web sites
More information
- Add-on Links
- Version
- 1.3.3
- Size
- 29.46 kB
- Last updated
- a month ago (24 Aug 2025)
- Related Categories
- Licence
- MIT Licence
- Version History
- Add to collection
Support this developer
The developer of this extension asks that you help support its continued development by making a small contribution.
Release notes for 1.3.3
Hi! This release has a few fixes and enhancements:
- Remember text box content when closing and reopening the edit panel.
- Better way of applying CSS while using !important tags.
- Fixed preview to clean the older version of CSS applied.
- Checkbox for "recursive" set to marked as default.
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