Override any web resource. Debug without deploying.
Intercept and replace JavaScript, CSS, API responses, and headers in your browser. Test fixes safely without pushing to production. Works on Chrome, Firefox, and Edge.
Chrome removed live JS editing in DevTools.
Starting with Chrome 142 (October 2025), Google permanently disabled the ability to live-edit JavaScript in the Sources panel. Chrome Local Overrides fails on sites with cache-busting URLs. Live Resource Overriderestores this workflow — and adds API mocking, header modification, and injection capabilities that DevTools never had.
Everything you need to debug in the browser
A complete toolkit for intercepting, replacing, and mocking web resources — without touching production code.
URL Pattern Matching
Match URLs by exact string, contains, wildcard, or full regex. Test patterns before saving.
6 Override Modes
Inline code, redirect URL, file upload, header modification, API mock, and script/style injection.
API Mocking
Return custom JSON responses with configurable HTTP status codes and content types.
Header Modification
Set, append, or remove request and response headers using declarativeNetRequest.
Rule Groups & Sharing
Organize rules into folders. Import/export rule sets as JSON to share with your team.
Cross-Browser
Works on Chrome 111+, Firefox 109+, and Edge 111+. One codebase, three browsers.
How it works
Three steps. No build tools. No proxy setup.
Install the Extension
Add Live Resource Override from the Chrome Web Store, Firefox Add-ons, or Edge Add-ons. Takes 10 seconds.
Create Override Rules
Set a URL pattern, choose your override type (code, redirect, mock, headers, inject), and paste your replacement.
Reload & Debug
Refresh the target page. Your override is active. The original resource is blocked at the network level and replaced with your version.
Browser Request ──▶ declarativeNetRequest ──▶ BLOCKED
│
▼
Content Script ──▶ Override Code INJECTED
(document_start) into page contextHow we compare
Free, open-source, and built for Manifest V3 from day one.
| Feature | LRO | Requestly | Resource Override | Charles/Fiddler |
|---|---|---|---|---|
| Price | Free | Freemium ($25/mo+) | Free | $50 / $250 |
| URL Pattern Matching | 4 modes | 4 modes | Contains only | Full regex |
| Override Types | 6 modes | 3 modes | 2 modes | 2 modes |
| API Mocking | Yes | Yes | No | Yes |
| Header Modification | Yes | Yes | No | Yes |
| Manifest V3 | Yes | Yes | No (MV2) | N/A |
| Open Source | Yes | No | Yes | No |
Stay in the loop
Get notified when we release new features, browser store updates, and tips.