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

RequestFox is a free API tester and network monitor for Chrome, Edge 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 leaves your device. NEW IN 2.2 • More room for your requests: a one-line recording bar and compact counters • Expired tokens explained: a 401 sent with an expired JWT says so, right on the request • N+1 detection: one endpoint called for id after id in a burst is flagged • Compose with simple name/value rows for params, headers and form fields • Copy any request as code in 15 languages, six of them new • Unset {{variables}} are caught before a request goes out; JSON bodies format in one click 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, OpenAPI specs and cURL commands • 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 • 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 • 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