# CORS Unblock

> No more CORS error by appending 'Access-Control-Allow-Origin: \*' header to local and remote web requests when enabled

Canonical page: [https://chrome-stats.com/d/cors-unblock](https://chrome-stats.com/d/cors-unblock)

## Overview

- **ID:** `cors-unblock`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Balvin
- **Category:** web-development,privacy-security
- **Daily users:** 6,333
- **Weekly downloads:** 171
- **Rating:** 3.74 / 5 (35 ratings)
- **Version:** 0.3.8
- **Last updated:** 2024-02-11
- **First published:** 2019-01-22
- **Size:** 206 KB
- **Data as of:** 2026-09-09
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/cors-unblock/)
- **Website:** [https://add0n.com/access-control.html](https://add0n.com/access-control.html)

## Description

CORS Unblock is a powerful Chrome extension designed to eliminate Cross-Origin Resource Sharing (CORS) errors by appending custom Access-Control-Allow-Origin and related headers to all browser requests. Users can easily toggle the extension on or off from the toolbar and customize allowed HTTP methods such as GET, PUT, POST, DELETE, and more through the context menu.

It supports a wide range of HTTP methods including WEBDAV-specific ones and provides configurable options to respect existing server headers or overwrite them. This extension is ideal for developers and testers working with cross-origin APIs or web services who need seamless control over CORS policies without server-side changes. Comprehensive documentation and bug reporting are available on its GitHub repository.

## Rankings

- #1,018 — Overall
- #100 — Web Development
- #216 — Privacy & Security
- #10 — unblock
- #31 — block ads
- #31 — writer's block

## Permissions and access

### Permissions

- `storage`
- `<all_urls>`
- `webRequest`
- `webRequestBlocking`
- `declarativeNetRequest`
- `contextMenus`

## Safety

- **Risk impact:** Moderate risk impact
- **Risk likelihood:** Low risk likelihood

### Analysis details

- Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
- This extension has low user count. Unpopular extensions may not be stable or safe.

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

## Review summary

Users generally praise CORS Unblock when it works, noting it does what it promises and can be a real time-saver for developers, with features like adjusting Access-Control-Expose-Headers. However, many reviews report reliability problems, with CORS requests still failing on numerous sites, and occasional breaks on services like YouTube. Some compatibility issues appear across Firefox versions (e.g., Firefox 86) or after updates. A common request is to add site whitelisting to limit the extension's effect to specific domains.

### Pros

- Works as intended when enabled; users report it turning on properly via the extension icon and it functioning well.
- Useful for testing and development; can save time for frontend work.
- Allows modifying Access-Control-Expose-Headers, a handy feature.
- Widely considered a needed and valuable CORS extension for Firefox when it works.

### Cons

- Unreliable or non-functional on many sites; reports of requests still failing.
- Can cause issues on some sites (e.g., breaks YouTube playback) and other compatibility problems.
- Lacks site whitelisting; users request the ability to restrict the extension to specific domains.
- Compatibility and timing issues across Firefox versions (e.g., reported problems around Firefox 86 and Sept 2023).

## Similar extensions and apps

- [CORS Unblock](https://chrome-stats.com/d/cors-unblock-enable-best) — 447 users
- [Allow CORS: Access-Control-Allow-Origin](https://chrome-stats.com/d/access-control-allow-origin) — 8,838 users, 2.68 / 5
- [CORS Unblock](https://chrome-stats.com/d/cors-unblock2) — 89 users, 5.00 / 5
- [CORS dev tool](https://chrome-stats.com/d/cors-dev-tool) — 13 users, 3.67 / 5
- [CORS Unbound](https://chrome-stats.com/d/cors-unbound) — 20 users
- [CORS Everywhere](https://chrome-stats.com/d/cors-everywhere) — 20,852 users, 4.13 / 5
- [CORSE](https://chrome-stats.com/d/corseverywhere) — 36 users
- [CORS Policy Header Viewer](https://chrome-stats.com/d/cors-policy-header-viewer) — 1 users
- [Custom CORS Control](https://chrome-stats.com/d/custom-cors-control) — 6 users
- [Moesif Origin & CORS Changer](https://chrome-stats.com/d/moesif-origin-cors-changer1) — 491 users, 3.00 / 5
- [Corsify](https://chrome-stats.com/d/corsify) — 1 users, 3.00 / 5
- [Safe CORS](https://chrome-stats.com/d/safe-cors) — 12 users

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Source: [Chrome-Stats](https://chrome-stats.com/d/cors-unblock)