Fast CORS Unblocker - Instant API Toggle

Easily unblock CORS restrictions, modify headers, and test APIs locally without server CORS errors. Lightweight & Manifest V3.

FAST CORS UNBLOCKER - INSTANT API TOGGLE & CORS HEADER MODIFIER Eliminate Cross-Origin Resource Sharing (CORS) restrictions and Access-Control-Allow-Origin errors during frontend web and API development in 1 click. Fast CORS Unblocker is a lightweight, developer-focused Manifest V3 extension designed to unblock local API development without configuring complex reverse proxies, modifying production backend code, or disabling your browser's security settings globally. WHY DEVELOPERS NEED A BETTER CORS UNBLOCKER: Most legacy CORS extensions inject wildcard headers globally across all browser tabs. This causes severe disruptions: messaging apps, video streaming services, social media feeds, and single-sign-on (SSO) login sessions break or log you out unexpectedly. Furthermore, older extensions frequently disable themselves after page reloads due to service worker dormancy bugs or leak excessive memory. Fast CORS Unblocker solves this with Smart Localhost Safe-Mode and Chromium's native declarativeNetRequest engine. It modifies response headers strictly on localhost, local IP addresses, and designated staging origins, leaving the rest of your web browsing 100% normal and secure. CORE DEVELOPER CAPABILITIES: • 1-CLICK MASTER TOGGLE Quickly enable or disable CORS header modifications from the toolbar popup or dockable side panel. Visual status badge confirms active protection at a glance. • SMART LOCALHOST SAFE-MODE Automatically scopes header rules strictly to localhost and 127.0.0.1. External websites, internal tools, and everyday browsing are never modified or disrupted. • 0MS NATIVE DECLARATIVENETREQUEST ENGINE Engineered 100% for Manifest V3. Uses Chromium's native C++ declarative network engine instead of heavy background proxy scripts. Zero latency overhead, zero CPU drain, and zero memory leaks. • AUTOMATIC OPTIONS PREFLIGHT HANDLING Seamlessly handles HTTP OPTIONS preflight requests by caching valid 200 OK responses, resolving complex preflight verification failures instantly. • FULL CREDENTIALS & COOKIE SUPPORT Injects Access-Control-Allow-Credentials: true and dynamically reflects the requesting origin so authenticated session cookies and Bearer tokens work smoothly in local development. • CUSTOM ORIGIN & REQUEST HEADER INJECTION Configure dynamic origin reflection or wildcard origins. Inject custom request headers such as Authorization, X-API-Key, or custom testing tokens with precision URL path matching. • BUILT-IN LIVE ENDPOINT CONNECTIVITY TESTER Verify whether your local or staging backend API is reachable with 1 click directly inside the extension popup before writing frontend code. • DOCKABLE CHROME SIDE PANEL Dock Fast CORS Unblocker alongside your DevTools, Swagger documentation, or local dev server for uninterrupted workflow integration. HOW TO USE: 1. Click the Fast CORS Unblocker icon in your browser toolbar. 2. Toggle the switch to ON. 3. Reload your local development page or re-trigger your fetch / XHR request. 4. Your API call completes successfully with valid Access-Control-Allow-Origin headers. FREE VS. PRO PRICING & IN-PRODUCT PURCHASES: Fast CORS Unblocker provides unlimited, free access for standard local development with an optional lifetime upgrade for advanced staging infrastructure: • Free Tier ($0 / Free Forever): - Unlimited 0ms CORS unblocking for localhost and 127.0.0.1. - Full Credentials and cookie support (Access-Control-Allow-Credentials: true). - Automatic OPTIONS preflight handling and caching. - Custom target origin configuration. - 1 active custom request header rule. - Built-in live endpoint connectivity tester. - Light and dark theme support. • Pro Tier ($19.50 USD One-Time Lifetime License): - Custom Domain Whitelisting: Unblock custom internal and remote staging domains (e.g., dev.company.internal, staging-api.net). - Unlimited simultaneous custom request header injection rules. - Advanced URL pattern filtering. - Valid on up to 3 personal devices (workstation, laptop, office). - Zero recurring monthly subscriptions. One payment, keep forever. PRIVACY & DATA SAFETY: • Zero Telemetry on API Payloads: Fast CORS Unblocker never intercepts, logs, or transmits your private API request bodies, headers, or responses to any external server. • 100% In-Memory Processing: All network rule modifications execute locally within Chromium's sandboxed network layer. • No Account Required: Start developing immediately without registering, creating accounts, or sharing email addresses. FREQUENTLY ASKED QUESTIONS: Q: Will this break my other browser tabs or websites? A: No. Unlike legacy extensions that apply wildcard rules to every URL, Fast CORS Unblocker defaults to Smart Localhost Safe-Mode, isolating rules exclusively to localhost and 127.0.0.1. Q: Does it turn off automatically when I reload the page? A: No. Dynamic rules are registered persistently with Chromium's declarativeNetRequest engine and remain active until you explicitly toggle them off. Q: Can I use custom Authorization or Bearer token headers? A: Yes. You can inject custom request headers with custom values directly from the popup.