Custom Site JS

Custom Site JS

Run your own (per url or domain) custom JavaScript on sites.

What is Custom Site JS?
Custom Site JS is a Firefox add-on that enables you to easily run personalized JavaScript on websites as they load. With the ability to add, edit, or delete JavaScript snippets based on URL, you can customize websites to your liking. The extension operates locally, ensuring your information remains secure.
Users: 218 ▲ 8
Rating: 4.80 (5)
Version: 1.0.1 (Last updated: 2019-10-29)
Creation date: 2019-10-29
Weekly download count: 20
Firefox on Android: No
Risk impact: High risk impact
Risk likelihood: Low risk likelihood
Manifest version: 2
  • webNavigation
  • storage
  • tabs
  • *://*/*
Size: 100.46K
Stats date:

Other platforms

Not available on Chrome
Not available on Edge
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Have you ever wished you could customize a website to your personal preferences every time you visited it?

Ever heard of a bookmarklet? Bookmarklets run JavaScript on a page for you when you click on the bookmark. But how inconvenient to have to click a bookmark every time you visit a site?

What if you could have your JavaScript simply run on the site as the page loads with no extra effort from you? That's what this extension is about.

Custom Site JS allows you to Add, Edit, or Delete snippets of custom JavaScript, that will automatically be run on a page for you based on a URL you provide. You can create as many as you like. The only limit is a maximum of 5 megabytes as the scripts are stored in your local storage.

Everything is stored and run locally. This extension will never make any kind of external web request, network requests, or in short send any of your information anywhere. The only way it will pass any information outside of your local environment is if you create a snippet of JavaScript that explicitly sends information somewhere.

User reviews
by HomerSETH9, 2023-12-21
View all user reviews
Risk impact

Custom Site JS 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 Custom Site JS if you trust the publisher.

Risk likelihood

Custom Site JS has earned a fairly good reputation and likely can be trusted.

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