# Style Engine – Custom CSS & JavaScript

> Apply custom CSS and JavaScript to websites globally or per domain. Lightweight, local-only, and fully user-controlled.

Canonical page: [https://chrome-stats.com/d/style-engine](https://chrome-stats.com/d/style-engine)

## Overview

- **ID:** `style-engine`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Glitchid
- **Category:** web-development
- **Daily users:** 4
- **Weekly downloads:** 1
- **Version:** 1.2.0
- **Last updated:** 2026-03-04
- **First published:** 2026-03-01
- **Size:** 102 KB
- **Data as of:** 2026-09-07
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/style-engine/)
- **Website:** [https://glitchid.com/products/style-engine/](https://glitchid.com/products/style-engine/)
- **Privacy policy:** [https://addons.mozilla.org/firefox/addon/style-engine/privacy/](https://addons.mozilla.org/firefox/addon/style-engine/privacy/)

## Description

Style Engine lets you apply your own CSS and JavaScript rules to websites. Built for developers, designers, and power users who want precise UI control without touching server-side code.

Apply custom CSS and JavaScript to websites globally or per domain. Lightweight, local-only, and fully user-controlled.

Key features

Global rules: Apply CSS/JS to all websites (typography tweaks, accessibility improvements, debugging overlays).
Per-website rules: Domain-isolated rule sets with independent enable/disable controls.
SPA navigation support: CSS automatically re-applies on route changes; JavaScript re-run can be enabled in Settings.
Optional live preview: Live JavaScript preview while typing in the popup editor (can be disabled in Settings).
Backup & Restore: Export/import your full configuration safely with a local JSON backup.
Flexible feedback: Desktop notifications, inline feedback, or silent mode.
Multi-language interface: English, Spanish, German, French, Italian, Dutch, Polish, Portuguese, Turkish, and Russian.

Common use cases

Create custom dark mode rules for sites that don’t support it.
Hide intrusive UI elements (banners, promos, sticky bars) with a few selectors.
Automate repetitive tasks with small JavaScript snippets.
Normalize fonts, spacing, and layout for a consistent browsing experience.

Privacy & safety

No tracking: Style Engine does not collect browsing data or analytics.
Local-only: Your rules are stored locally in your browser.
User-controlled: The extension runs only the code you explicitly write and save.
No remote code: No external scripts are downloaded or executed.

Links

Website: <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/dda85994c37045f14a71da187cb2fac0216554d4971797c12273f493a11e726f/https%3A//glitchid.com/products/style-engine/" rel="nofollow">https://glitchid.com/products/style-engine/</a>
Documentation: <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/5a0bca9247ddd515f16f700553a4c1e8dfd1b94f80775a4859ec27ef96668ec3/https%3A//glitchid.com/products/style-engine/documentation/" rel="nofollow">https://glitchid.com/products/style-engine/documentation/</a>
Privacy: <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/abc5e96dedd8d6053d08da91afa0456e56a66dfd46dd6a1344b6d91093c61516/https%3A//glitchid.com/privacy/style-engine-privacy/" rel="nofollow">https://glitchid.com/privacy/style-engine-privacy/</a>
Terms: <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/c4046401c9db32096f6e313dc17df04ceb0aac61d50a71a3fc5ff0758393d903/https%3A//glitchid.com/terms/style-engine-terms/" rel="nofollow">https://glitchid.com/terms/style-engine-terms/</a>
Support: support@glitchid.com

Publisher: Glitchid

## Rankings

- #48,446 — Overall
- #31 — javascript
- #157 — engine
- #168 — script
- #201 — style
- #246 — custom feed

## Permissions and access

### Permissions

- `storage`
- `notifications`
- `scripting`
- `activeTab`

### Content script matches

- `<all_urls>`

## Safety

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

### Analysis details

- Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
- 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/style-engine)