CustomCSS Injector

CustomCSS Injector

- Apply any CSS rules for any websites, including iframes. - Whitelist and Blacklist functionality - Apply CSS rules to specific URLs, Domains or Globally - Syntax highlighting & line numbers - Update without page refresh

What is CustomCSS Injector?

CustomCSS Injector is a unique Firefox add-on, powerfully designed to let you customize the appearance of any website as per your preference. It provides you with the power to change colors, backgrounds, resize elements and even hide those you find intrusive, all by applying your own CSS rules. The add-on includes features such as applying CSS rules based on specific URLs, Domains or Globally, coupled with a whitelist/blacklist functionality. Further enhancing your experience are syntax highlighting and line numbers courtesy of PrismJS, making your coding readable and accessible.

Stats date:
By: Blizz3
Users: 1,128 ▲ 20
Rating: 4.50 (16)
Version: 1.3.2 (Last updated: 2020-04-02)
Creation date: 2019-07-06
Weekly download count: 49
Firefox on Android: Yes
Manifest version: 2
  • storage
  • <all_urls>
  • contextMenus
  • notifications
Size: 44.31K
Email: Click to see
URLs: Website
Risk impact: High risk impact
Risk likelihood: Low risk likelihood

Other platforms

Not available on Chrome
Not available on Edge

Custom CSS Injector lets you write any CSS rules and apply them to any website you like. Change colours, backgrounds, resize and hide obtrusive elements. Anything you can do within the power of CSS! Simply write the CSS you want to apply in the provided text field and click 'Save' (NO page refresh required!). Apply the CSS to the URL, Domain or Globally by using the radio buttons provided. There is also a whitelist/blacklist functionality to govern which websites you'd like to apply the CSS to. Enjoy syntax highlighting and line numbers for code readability (Thanks to PrismJS!)

User reviews
User reviews summary
These summaries are automatically generated weekly using AI based on recent user reviews. Firefox Browser Add-ons does not verify user reviews, so some user reviews may be inaccurate, spammy, or outdated.
  • Easy to use
  • Powerful
  • Able to override offending CSS
  • Lightweight and straightforward
  • Makes work much easier
  • Delay in CSS injection
  • Doesn't seem to work initially
  • Invalid data error with no feedback
Most mentioned
  • Easy to use
  • Powerful
  • Delay in CSS injection
  • Fixes CSS issues
  • Needs support for Firefox for Android
View all user reviews
Risk impact

CustomCSS Injector is risky to use as it requires a number of sensitive permissions that can potentially harm your browser and steal your data. Exercise caution when installing this add-on. Review carefully before installing. We recommend that you only install CustomCSS Injector if you trust the publisher.

Risk likelihood

CustomCSS Injector has earned a fairly good reputation and likely can be trusted.

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