Mockrew: Mock & Rewrite HTTP requests

Mock & rewrite HTTP requests in DevTools, modify headers and redirect URLs at the browser network layer.

Mockrew mocks and rewrites API traffic without changing the application you are testing. Interception runs inside the page and in the browser's network request layer, so rules stay active whether DevTools is open or not. The DevTools panel is where you manage rules and inspect the requests that hit them. USE CASES • Start the frontend before the API exists. Return realistic payloads from Faker templates and keep building while the backend catches up. • Reproduce the states that are awkward to create by hand: empty lists, slow responses, 500s, expired tokens, the last page of a paginated list. • Walk through a multi-step flow without resetting the backend. A sequenced response moves the state forward on every poll: queued, running, done. • Move one URL without touching the app: redirect it to staging, to another origin or to a local server — no code change, no rebuild. • Give each tenant, locale or role its own data by branching on a request header or a query parameter. • Share the setup. Export rules as JSON and a teammate imports the same file to reproduce your environment. FEATURES • Mock responses for fetch and XMLHttpRequest: status code, delay and JSON body. • Method and URL matching: contains, path parameters, exact match or regular expression. • Conditions on query parameters, request headers or the JSON body (dot path); every condition must match before a rule fires. • GraphQL: match on operation type, operation name, query text or variables, and write only the payload — the response is wrapped into { data } for you. • Sequenced responses: a different result on each hit, stopping at the last step or looping. • Data generation from Faker templates such as {{person.fullName}} or {{internet.email}}. • JS hooks for responses that depend on the request. • Rewrite only what you need and let the real request go out: URL, query string, request body, request headers, response headers or response body — declaratively, or with request / response JS hooks. • Header changes and URL redirects in the browser's network request layer, applied before the request leaves the browser and covering every request type, including subresources and page navigations. • A request log with the matched rule and sequence step, plus one-click rule creation from a logged request. • Projects, drag-and-drop ordering, and on/off switches at the global, project and rule level. • Import rules from an OpenAPI / Swagger document, a Postman collection or a Mockrew JSON file — each endpoint becomes a rule with a response body taken from the spec — and export back to JSON. JS HOOKS: WHEN A TEMPLATE ISN'T ENOUGH Templates cover the responses you can write down in advance. In practice, the harder case is the reverse: the body has to be computed from the request in front of you. That is what JS hooks are for. A hook receives the request — URL, method, headers, query, body and path parameters — and returns the response, with async/await available for anything that needs to be awaited. Sign a payload with the current timestamp, echo an id from the body into a nested field, decide the next page from a cursor, or derive a permission list from the role in the token. Rewrites work the same way: when a declarative rule cannot express the change, use a request or response hook instead. PRIVACY Your API traffic stays in your browser. Rules, responses and scripts are stored in local extension storage; request URLs, headers and bodies are never uploaded. The Free plan needs no account, and core mocking works offline. Mockrew asks for access to all sites because the interceptor has to run on whatever page you are debugging. The permission is used only to install that interceptor; page content is never collected or transmitted. PLANS Free: up to 2 projects, 20 rules in total and 5 active rules at a time, with mock responses, rewrites, Faker templates, header changes, redirects and request logging. Pro: unlimited projects and rules, plus sequenced responses, JS hooks and rewrite hooks. A 7-day trial is available. GOOD TO KNOW • Mock response bodies and rewrites apply to fetch and XMLHttpRequest. Header changes and URL redirects run in the browser's network request layer and cover all request types. • Requests from Web Workers, a page's own Service Worker and synchronous XHR are not intercepted. • Requires Chrome version 116 or later. Website: https://mockrew.com Guide: https://mockrew.com/guide Privacy policy: https://mockrew.com/privacy Support: support@mockrew.com