Per-Domain User CSS od ArachnidFight

Per-Domain User CSS lets you restyle websites exactly how you want. If a page uses an unreadable font or bright background, you can fix it instantly. The extension stores your custom CSS separately for each exact domain (for example, test.example.com and example.com are treated independently).

Features

• Apply custom CSS per exact domain or subdomain.
• Toggle styles on or off anytime.
• Preview your changes before saving.
• Optionally auto-add !important to each rule.
• Simple popup interface with textarea editor.

Lightweight and private — all data stored locally.

How it works

• Open a site and click the extension icon.
• Write your CSS in the popup.
• Click Preview to test or Save to store it.
• Enable/disable with the checkbox.

The extension injects your CSS automatically each time you visit that same domain.
It never sends data anywhere and requires no network access.