# Per-Domain User CSS

> Add custom CSS per domain. Modify fonts, colors, and layouts on any website. Each domain has its own saved style. Includes enable/disable toggle, preview, and save options.

Canonical page: [https://chrome-stats.com/d/per-domain-user-css](https://chrome-stats.com/d/per-domain-user-css)

## Overview

- **ID:** `per-domain-user-css`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** ArachnidFight
- **Category:** web-development,appearance
- **Daily users:** 20
- **Weekly downloads:** 3
- **Version:** 1.0.1
- **Last updated:** 2025-11-06
- **First published:** 2025-11-03
- **Size:** 14 KB
- **Data as of:** 2026-09-14
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/per-domain-user-css/)

## Description

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, <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/071b05eb1c8c4dc768936b1fa46fa22e75002b0e60ff5e83d8640122e78fa19f/http%3A//test.example.com" rel="nofollow">test.example.com</a> and <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/2141eac2eacda036b00afc30fd0a7e6f24e9bddf402cf4393fe5144f468147e8/http%3A//example.com" rel="nofollow">example.com</a> are treated independently).

Features
<ul><li>Apply custom CSS per exact domain or subdomain.</li><li>Toggle styles on or off anytime.</li><li>Preview your changes before saving.</li><li>Optionally auto-add !important to each rule.</li><li>Simple popup interface with textarea editor.</li></ul>
Lightweight and private — all data stored locally.

How it works
<ul><li>Open a site and click the extension icon.</li><li>Write your CSS in the popup.</li><li>Click Preview to test or Save to store it.</li><li>Enable/disable with the checkbox.</li></ul>
The extension injects your CSS automatically each time you visit that same domain. 
It never sends data anywhere and requires no network access.

## Rankings

- #24,983 — Overall
- #25 — domain

## Permissions and access

### Permissions

- `storage`
- `tabs`
- `<all_urls>`

### Content script matches

- `<all_urls>`

## Safety

- **Risk impact:** High risk impact
- **Risk likelihood:** Moderate risk likelihood

### Analysis details

- Grants access to browser tabs, which can be used to track user browsing habits and history, presenting a privacy concern.
- This extension has low user count. Unpopular extensions may not be stable or safe.

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

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Source: [Chrome-Stats](https://chrome-stats.com/d/per-domain-user-css)