Firefox Browser Add-ons
  • Extensions
  • Themes
    • for Firefox
    • Dictionaries & Language Packs
    • Other Browser Sites
    • Add-ons for Android
Log in
Preview of JShelter

JShelter by Libor Polčák

JShelter controls the APIs provided by the browser. The goal is to improve the privacy and security of the user running the extension.

Available on Firefox for Android™Available on Firefox for Android™
4.5 (44 reviews)4.5 (44 reviews)
448 Users448 Users
You'll need Firefox to use this extension
Download Firefox and get the extension
Download file

Extension Metadata

Screenshots
You can disable Geolocation or JSR can fake your location according to your preference.Test pagePopupDetail view on APIs used by the visited pageOption page, show levelYou can see a report on fingerprinting activities by the page
About this extension
What is JShelter?

JShelter is a browser extension to give back control over what your browser is doing. A JavaScript-enabled web page can access much of the browser's functionality, with little control over this process available to the user: malicious websites can uniquely identify you through fingerprinting and use other tactics for tracking your activity. JShelter aims to improve the privacy and security of your web browsing.


How does it work?

Like a firewall that controls network connections, JShelter controls the APIs provided by the browser, restricting the data that they gather and send out to websites. JShelter adds a safety layer that allows the user to choose if a certain action should be forbidden on a site, or if it should be allowed with restrictions, such as reducing the precision of geolocation to the city area. This layer can also aid as a countermeasure against attacks targeting the browser, operating system or hardware.

Please see the FAQ (https://jshelter.org/faq/) and our blog (https://jshelter.org/blog/) for more information about the extension.

What is the threat model?

See https://jshelter.org/threatmodel/

Do you have a paper that explains the extension?

Yes, see https://arxiv.org/abs/2204.01392
Developer comments
Report a bug: https://pagure.io/JShelter/webextension/issues, https://github.com/polcak/jsrestrictor/issues
Rated 4.5 by 44 reviewers
Log in to rate this extension
There are no ratings yet

Star rating saved

5
33
4
4
3
3
2
2
1
2
Read all 44 reviews
Permissions and dataLearn more

Required permissions:

  • Display notifications to you
  • Access browser tabs
  • Access browser activity during navigation
  • Access your data for all websites

Optional permissions:

  • Clear recent browsing history, cookies, and related data
More information
Add-on Links
  • Homepage
  • Support site
  • Support Email
Version
0.21
Size
467.2 KB
Last updated
2 months ago (Jun 17, 2025)
Related Categories
  • Web Development
  • Privacy & Security
License
GNU General Public License v3.0 only
Version History
  • See all versions
Tags
  • anti malware
  • anti tracker
  • privacy
  • security
Add to collection
Report this add-on
Release notes for 0.21
  • Add support for Temporal.Now.instant() that provides precise timestamps
  • Refactor code for modifications of timestamps to be more readable as well faster
More extensions by Libor Polčák
  • There are no ratings yet

  • There are no ratings yet

  • There are no ratings yet

  • There are no ratings yet

  • There are no ratings yet

  • There are no ratings yet

Go to Mozilla's homepage

Add-ons

  • About
  • Firefox Add-ons Blog
  • Extension Workshop
  • Developer Hub
  • Developer Policies
  • Community Blog
  • Forum
  • Report a bug
  • Review Guide

Browsers

  • Desktop
  • Mobile
  • Enterprise

Products

  • Browsers
  • VPN
  • Relay
  • Monitor
  • Pocket
  • Bluesky (@firefox.com)
  • Instagram (Firefox)
  • YouTube (firefoxchannel)
  • Privacy
  • Cookies
  • Legal

Except where otherwise noted, content on this site is licensed under the Creative Commons Attribution Share-Alike License v3.0 or any later version. Android is a trademark of Google LLC.