Style Engine

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

Style Engine lets you apply your own CSS and JavaScript rules to websites.

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Platforms:

Google Chrome Microsoft Edge Mozilla Firefox Opera Browser

Category: Extension

Product type: Free

Latest version: v1.2.0

Last updated: 2026-02-28

Status: Available to install.

Downloads

Microsoft Edge

Mozilla Firefox

Google Chrome

Screenshots

Overview

Take complete control of the web.

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

What It Does

  • Inject custom CSS into any site
  • Run custom JavaScript in the page context
  • Apply rules globally across all websites
  • Create isolated per-domain rule sets

All rules are stored locally and applied only where you enable them.

Key Features

  • Site-Specific Rules — Create isolated CSS and JS rules per domain with independent enable/disable controls.
  • Global Mode — Apply rules across your entire browsing experience (typography tweaks, accessibility, debugging overlays).
  • SPA Navigation Support — Route-change aware re-application for modern single-page apps. CSS always re-applies; JavaScript re-run is optional.
  • Live Preview (Optional) — Enable live JavaScript preview while typing in the editor (toggle in Settings).
  • Built-in Editor — Clean popup editor with structured modes: Global CSS / Global JS / Site CSS / Site JS.
  • Backup & Restore — Export and import your configuration safely using a local JSON file.
  • Flexible Feedback — Choose desktop notifications, inline feedback, or silent mode.

Use Cases

  • Create a custom dark mode for sites that don’t support it
  • Hide intrusive elements, banners, or overlays
  • Improve readability and accessibility
  • Automate repetitive UI tasks
  • Test layout and style experiments without touching backend code

Privacy & Safety

Style Engine operates entirely locally.

  • No tracking
  • No analytics
  • No remote code execution
  • No external data transmission

The extension injects only the code you explicitly write and save.

For more info: Privacy Policy | Terms of Service

Performance

Built with Manifest V3 and optimized for minimal overhead, Style Engine runs efficiently without slowing down your browser.

A Glitchid product.

Keywords: css injector, javascript injector, custom stylesheet, web customizer, userstyles alternative, script runner, dark mode creator, browser customization tool

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