EchoKit is a zero-setup Chrome extension. Record real API traffic from any tab, then instantly mock any of it back with strict matching, latency & error simulation, and a raw JSON editor. No backend. No accounts. No telemetry.
Open any tab → hit ● REC → use your app → flip MOCK → edit → reload.
EchoKit hooks window.fetch and XMLHttpRequest from a MAIN-world content script. Every call on the recording tab is captured into IndexedDB — URL, method, headers, body, status, response — all of it.
Tap any request. Rewrite the JSON body, change the status, tweak headers. Pick a match mode: strict, ignore-query, ignore-body, path-wildcard, or GraphQL.
Flip the MOCK switch. The page hits your edits instead of the network. A huge amber banner means you never forget you're in mock mode.
method + normalized URL + normalized body. Query params are sorted, JSON bodies are canonicalized. Never ghost-mock the wrong endpoint.urlFilter pattern via declarativeNetRequest. No mock needed.Access-Control-Allow-* headers into real responses.localStorage to the clipboard. Paste into another tab with a one-click confirmation dialog.chrome://extensions/shortcuts.Everything you record lives in your browser's IndexedDB. No backend, no accounts, no telemetry. Uninstall to wipe. Read the full privacy policy →