Custom CSS

Custom CSS

Overwrite or inject custom CSS into website.

What is Custom CSS?

Custom CSS is a Firefox add-on by Kenny Ooi. This add-on has 86 daily active users and an average user rating of 2.60. The latest version, 1.1, was updated a year ago.

Stats date:
Users: 86 ▼ -3
Rating: 2.60 (5)
Version: 1.1 (Last updated: 2022-01-12)
Creation date: 2022-01-11
Weekly download count: 10
Firefox on Android: No
Manifest version: 2
  • tabs
  • storage
  • http://*/
  • https://*/
Size: 27.77K
Email: Click to see
Risk impact: High risk impact
Risk likelihood: Moderate risk likelihood
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Other platforms

Not available on Chrome
Not available on Edge
A simple plugin which allow web developer or those who familiar with CSS to inject own custom CSS into any website to overwrite default styling, such as font-size, font-color, and so on.
Risk impact

Custom CSS requires a number of risky 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 Custom CSS if you trust the publisher.

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, bypass your security settings, and access your personal data. High risk impact extensions are not necessarily malicious. However, if they do turn malicious, they can be very harmful.

Risk likelihood

Custom CSS is probably trust-worthy. Prefer other publishers if available. Exercise caution when installing this add-on.

Risk likelihood measures the probability that a Firefox add-on may turn malicious. This is determined by the publisher and the Firefox add-on reputation on Firefox Browser Add-ons, the amount of time the Firefox add-on has been around, and other signals about the Firefox add-on. 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 Firefox add-on, especially ones with higher risk impact and/or higher risk likelihood.

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User reviews
Throws all kinds of errors for no reason, even with basic elements like #header. It doesn't have any formatting aids either, though I suppose if all you care about is size that's not a dealbreaker.
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