User JavaScript and CSS

Name: User JavaScript and CSS
Rating: 4.788685524126456 (601 reviews)
Author: tenRabbits

User JavaScript and CSS on any website

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User JavaScript and CSS is a powerful Chrome extension for users to seamlessly inject their own JavaScript or CSS rules onto any webpage. It supports instant execution of scripts and styles, URL masking to apply rules across multiple sites, and inclusion of custom libraries for advanced functionality. Users can manage scripts with a clean UI, utilize SASS support, and take advantage of live CSS reloading for real-time design tweaks.

The extension offers robust features such as iframe injections, multi-URL rule support, and various editor enhancements including syntax highlighting and formatting. Regular updates ensure improved CSS injection and script handling. Comprehensive documentation is available to guide users in creating and applying custom scripts and styles tailored to enhance their browsing experience.

Extension Productivity Developer Tools

By:

Users:

Rating:

Version:

3.0.6 Last updated: 2025-02-07

Creation date:

2020-05-08

Risk:

Permissions:

storage
tabs
unlimitedStorage
userScripts
scripting

Host permissions:

http://*/
https://*/

Size:

1.62MB

Email:

sq*****@yandex.ru

Full description:

Source:

Chrome Web Store

Updated:

18 hours ago

Ranking

# 1,522 ▼ 9

Other rankings

#2623 in Developer Tools

#1 in javascript keyword 44

#6 in css editor keyword 30

#11 in jquery keyword 15

#21 in inject keyword 8 ▲ 1

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User reviews

Users praise 'User JavaScript and CSS' for its combined JS and CSS support, ease of use, and stability, making it ideal for customizing websites. Common issues include the need to reload pages for CSS changes, unreliable cloud sync, difficulty sharing scripts, occasional JavaScript execution problems, and limited editor customization. Overall, it's considered a powerful and user-friendly extension beloved by users who know a bit of code.

Pros

Supports both JavaScript and CSS/SCSS together in one extension
Easy-to-use, color-coded text editor with good UX and dark themes
Allows creating multiple scripts per website with toggling on/off
Stable and works well out of the box for customizing browsing experience
Free and powerful for users familiar with coding looking to customize sites

Cons

Needs page reload each visit for CSS changes to apply
Cloud synchronization does not work or is unreliable
No easy way to share or export user scripts and styles
JavaScript execution sometimes problematic or not working as expected
Limited editor customization options (e.g. font choice, vertical split)

Recent reviews

Really useful and cool extension!

Dm*****, 2025-06-19

Awesome, it works great! Thank you <3

SA*****, 2025-06-10

Why do I have to reload the page every time I visit it for the CSS to load?

Ka*****, 2025-06-10

View all user reviews ›

Extension safety

Risk impact

Risk impact measures the level of extra permissions an extension has access to. A low risk impact extension cannot do much harms, whereas a high risk impact extension can do a lot of damage like stealing your password, bypassing your security settings, and accessing your personal data. High risk impact extensions are not necessarily malicious. However, if they do turn malicious, they can be very harmful.

User JavaScript and CSS requires some sensitive permissions that could impact your browser and data security. Exercise caution before installing.

Risk impact analysis details

Critical Grants access to browser tabs, which can be used to track user browsing habits and history, presenting a privacy concern.
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Risk likelihood

Risk likelihood measures the probability that a Chrome extension may turn malicious. This is determined by the publisher and the Chrome extension reputation on Chrome Web Store, the amount of time the Chrome extension has been around, and other signals about the Chrome extension. Our algorithms are not perfect, and are subject to change as we discover new ways to detect malicious extensions. We recommend that you always exercise caution when installing a Chrome extension.

User JavaScript and CSS is probably trust-worthy. Prefer other publishers if available. Exercise caution when installing this extension.

Risk likelihood analysis details

High This extension has low user count. Unpopular extensions may not be stable or safe.
Low **** ********* *** ******* **** **** * ****** **** ***** ******** *** **** ****** ** ** ****** *** *****
Low **** ********* *** ***** **** **** * ****** **** ***** ********** *** **** ****** ** ** ****** *** *****
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