Syncmock

Intercept, inspect, and mock HTTP requests in your browser. Mock REST and GraphQL APIs without a proxy or backend changes.

Syncmock is a developer tool for intercepting, inspecting, and mocking HTTP traffic directly in your browser — no proxy, no certificates, no backend changes. WHAT YOU CAN DO • Mock REST APIs — return any JSON body, status code, and headers • Mock GraphQL — match on operation names, return custom envelopes • Override response bodies — let the real request fly, then swap the response • Override request bodies — modify outgoing payloads before they're sent • Redirect URLs — reroute requests to a different host, path, or port • Modify headers — inject, override, or remove request/response headers • Delay requests — simulate slow networks • Live capture — watch every fetch and XHR in real time RESPONSE VARIANTS Keep success, empty, error, and edge-case responses on a single rule and switch between them instantly. No rule sprawl. RULE ENGINE 6 matcher types (URL contains, regex, domain, HTTP method, header, GraphQL operation) combined with 8 action types. Priority ordering decides which rule wins. PRIVACY Everything runs locally. Rules and captured traffic stay in your browser's local storage. No account, no cloud sync, no telemetry. Optional AI rule authoring uses an endpoint and API key you supply. REQUIREMENTS Chrome 116+ or any Chromium browser supporting Manifest V3.