CORS Everywhere

Name: CORS Everywhere
Rating: 4.1261 (119 reviews)
Author: spenibus

A firefox addon allowing the user to enable CORS everywhere by altering http responses. Report issues to the repository, with enough information to reproduce the problem: https://github.com/spenibus/cors-everywhere-firefox-addon/issues

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Features & Capabilities

CORS Everywhere is a Firefox addon designed for web developers needing to bypass Cross-Origin Resource Sharing (CORS) restrictions during testing and development. By altering HTTP responses, it enables CORS everywhere without disabling Firefox's inherent security features. The addon modifies HTTP headers to make browsers treat external resources as accessible, provided the requests conform to valid CORS rules.

This WebExtension can be toggled via a toolbar button with three states: disabled (red), enabled (green), and enabled with whitelist filters (green/red) for selective CORS bypassing. It includes customizable options for startup behavior, forced access-control header values, and regex-based activation whitelists. While primarily for desktop Firefox, Android support is untested and not officially supported. Users should exercise caution and use it at their own risk during development workflows.

User Growth & Download Statistics

Add-on Developer Tools Programming

By:

Daily users:

Rating:

Version:

18.11.13.2044resigned1 Last updated: 2024-04-25

Version code:

5726488

Creation date:

2015-09-10

Risk:

Permissions:

Size:

18.49KB

URLs:

Website

Full description:

Source:

Firefox Add-ons Store

Data ingested on:

2026-06-23

Compare stats and ranking:

Ranking

# 478 ▼ 5

Other rankings

#38 in Web Development ▲ 1

#61 in Other extensions

#117 in Privacy & Security ▼ 3

#49 in course keyword 11 ▼ 2

#54 in response keyword 16 ▼ 1

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For Developers

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Contact the developer

Chrome-Stats does not own this Firefox add-on. Please use these information below to contact the Firefox add-on developer.

Developed by:

spenibus

Firefox Add-ons Store

https://addons.mozilla.org/firefox/addon/cors-everywhere/

Website:

https://github.com/spenibus/cors-everywhere-firefox-addon/

User Reviews

Reviews cluster into two camps: many users praise its simplicity and ability to remove CORS issues with a one-click toggle, calling it convenient and practical, while several users report it fails on some sites or Firefox versions and can behave inconsistently compared with other CORS extensions.

Pros

Effectively bypasses CORS for many users — several reviewers say “it works”
Very simple to use: one-click toggle with no configuration or rulesets needed
Convenient and practical — many call it useful or a must-have for quick testing

Cons

Does not work for some users/sites or on certain Firefox versions (multiple reports)
Inconsistent behavior — results vary by site, version, or compared to other CORS extensions
Reliability is mixed: many praise it, but a noticeable subset report failures

Recent reviews

by Fi*****, 2026-03-21

by Jo*****, 2026-02-17

by *****, 2025-11-06

View all user reviews ›

Is CORS Everywhere Safe?

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.

CORS Everywhere requires a few sensitive permissions. Exercise caution before installing.

Risk impact analysis details

Critical Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
High ****** *** ********* ** ******* *** ******* ******* ** ****** *** *** ******** ******

Risk likelihood

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 Add-ons Store, 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.

CORS Everywhere has earned a fairly good reputation and likely can be trusted.

Risk likelihood analysis details

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