RequestFox – API Tester & Network Monitor: Capture, Replay, Mock

See every API call as you test. Auto-flags failed, slow & duplicate requests. Replay, mock & export to Postman — free, 100% local.

RequestFox is a free API tester and network monitor for Chrome and Firefox. It watches every API call your web app makes while you test it, and flags the failed, slow and duplicate ones for you, tied to the click that caused them. Compose and send requests, mock responses, and export tests and reports. No account; nothing is sent to us. NEW IN 2.3 • JSON answers as a tree: filter it, and click any value to copy it, check it or save it as a variable • Recent: your last 100 sends with their answers, kept on this device and ready to reopen • Collection and folder settings: variables, a base URL, headers and auth that every request inside uses • A command-line tool for CI ships inside the extension: export a suite and run it with Node 18 or newer • /users/1 and /users/2 count as one endpoint, and a changed response is caught deep in nested data and lists • Calls show up the moment they start, streams are captured, and failed calls say what went wrong in plain words • With nothing recording, Compose, saved requests and test suites send from the extension itself, without any page's cookies • Secret variables: a value kept encrypted in the vault, masked, and left out of environment exports and Copy as code WHAT IT CATCHES, AUTOMATICALLY • Failed calls: every 4xx/5xx and dropped connection, tied to the click or form submit that caused it • Errors hiding inside a 200 OK: GraphQL and JSON-RPC error responses • Slow responses, against a threshold you set • Duplicate calls: rapid double-fires and retries • N+1 bursts, and endpoints that keep failing • API contract drift: an endpoint's response shape changing mid-session • Expired bearer tokens behind a 401 or 403 SEE WHERE THE TIME WENT • Per-request timing: DNS, connect, TLS, waiting for the server, download • HTTP version, and bytes on the wire vs. decoded • "Called from": the page code that made the call • A waterfall timeline of the whole session MOCK, BREAK AND REWRITE • Mock any captured response in one click, with its real status, headers and body • Fail a call like a dropped connection, add delay or throttle it, or pause and edit a request or its reply • Set or remove request and response headers and rewrite URLs, with a simple form, no syntax to learn COMPOSE, IMPORT AND SEND • Send requests through the page you're testing, with its own cookies and session • Params, headers and form fields as rows; raw, URL-encoded and multipart bodies with files • The common auth types, including OAuth 2.0, and a GraphQL mode • Environments with {{variables}} and dynamic values • Import collections from other API clients (with their variables, auth and simple tests), OpenAPI specs and cURL commands • Collection and folder settings, and Recent: your last 100 sends with their answers • JSON answers as a tree you can filter, copy from, check or save as a variable • Copy any request as code in 15 languages • A WebSocket client, and every WebSocket and SSE frame the page sends or receives TURN A SESSION INTO TESTS • Chain saved requests into repeatable suites with pass/fail per step, and data-driven runs • Assertions on status, latency, fields, headers or a JSON Schema • Chain values from a response body, header or cookie into the next request • Run the same suites in CI with the one-file command-line tool the extension hands out • Export end-to-end tests for Playwright or Cypress, and load-test scripts TAKE THE EVIDENCE WITH YOU • An HTML report, a HAR file, a Postman collection, or an API spec built from what you captured • Compare two requests, or two sessions, side by side • Past sessions keep every body and screenshot, on this device • One-click GitHub or Linear issues with a ready-made repro PRIVATE BY DESIGN • No account, no cloud, no telemetry: everything stays in your browser • Tokens, cookies and passwords are redacted by default • Free, with a written promise that nothing free today gets paywalled • 14 languages, light and dark themes, keyboard and screen-reader friendly