API Override

Redirect requests, rewrite URLs, and mock API responses with a configurable rule list.

API Override is a developer tool for intercepting and modifying network requests in the browser. Build a list of rules, toggle them on or off individually, and reshape traffic without touching your application code. ━━━━━━━━━━━━━━━━━━ What you can do ━━━━━━━━━━━━━━━━━━ ▸ Redirect Request — match a URL with a regular expression and send it somewhere else. Capture groups in the match (\1, \2, …) are usable in the target. Perfect for pointing a production API at a local dev server, or swapping one CDN for another. ▸ Replace String — plain find-and-replace inside the URL, no regex needed. Quick way to swap a hostname, force HTTPS, or change an API version. ▸ Query Param — add, replace, or remove a query parameter on matching requests. Useful for injecting debug flags, stripping tracking parameters (utm_*), or appending a cache-buster. ▸ Modify Response — return a custom status code, content-type, and body for matching requests. The request never hits the real server. Great for mocking an unbuilt endpoint, simulating a 500 error to test failure paths, or stubbing out analytics calls with an empty 204. ━━━━━━━━━━━━━━━━━━ Why you'd want it ━━━━━━━━━━━━━━━━━━ • Front-end work against an API that isn't ready yet — mock it. • Reproduce a bug that only happens when an endpoint returns a specific error. • Demo or QA a build against a different backend without rebuilding the bundle. • Strip tracking parameters from the URLs you click. • Test how your app behaves when a third-party script fails to load. ━━━━━━━━━━━━━━━━━━ How it works ━━━━━━━━━━━━━━━━━━ Redirect, Replace String, and Query Param rules run on Chrome's native declarativeNetRequest engine — fast, and they don't read the contents of any request. Modify Response rules use the Chrome DevTools Protocol (the "debugger" permission) because that is the only API capable of substituting a response body in Manifest V3. While at least one Modify Response rule is enabled, Chrome shows its standard "this browser is being debugged" notice. Disable or delete those rules (or flip the master toggle off) and the notice disappears immediately. A master switch in the popup turns everything off without losing your rules. Each rule also has its own enable/disable toggle. Rules apply top-to-bottom; conflicting rules are resolved by list order. Changes save automatically. ━━━━━━━━━━━━━━━━━━ Privacy ━━━━━━━━━━━━━━━━━━ API Override does not collect, transmit, or store any browsing data on remote servers. Your rules are saved locally in Chrome's extension storage, on your machine. Nothing leaves the browser.