Net Tinker

Mock, redirect, delay or rewrite HTTP requests from the browser. No backend, no account, everything stays on your machine.

Net Tinker lets you intercept fetch and XHR requests and change what happens to them — without touching your backend, without an account, and without anything leaving your machine. WHAT YOU CAN DO • Mock a response — return your own status, headers and body. The request never reaches the network. • Change the real response — find and replace text in it, or overwrite a single JSON field and leave everything else exactly as the server sent it. • Modify a real request — change its body, its headers, or its query parameters, and let it go out as usual. • Redirect a request to a different URL, or rewrite part of the URL. • Block a request entirely. • Delay a request to see how your UI behaves on a slow connection. HIT EXACTLY THE REQUESTS YOU MEAN Match by URL or host — contains, exact, regex or wildcard — then narrow it down by HTTP method, by a request header, by what's in the request body, or by which page is making the call. Pin a rule to a single tab when you don't want it affecting everything else you have open. And because GraphQL sends every operation to the same endpoint, matching on the body is what finally lets you mock one operation without touching the rest. REUSE THE SAME RULES EVERYWHERE Write {{variables}} into bodies, headers, redirect URLs and query parameters, then define environments — Local, Dev, Staging, Prod — that override only the values which actually change. Switch between them from the popup, and the same set of rules follows you from localhost to staging. BUILD RULES FROM REAL TRAFFIC Net Tinker adds a panel to Chrome DevTools listing the requests of the page you are inspecting. One click turns any of them into a rule — and "Mock" fills in the real status, headers and response body for you, so you start from what the server actually returned instead of typing a fixture by hand. GraphQL operation names are detected and shown, so a list of calls to a single /graphql endpoint is finally readable. Any captured request can also be copied as a curl command or as a fetch() call. STAY IN CONTROL • Group rules and switch a whole group on or off in one click. STAY IN CONTROL • Group rules and switch a whole group on or off in one click. • Select several rules at once to enable, disable, export or delete them together. • See exactly which rule touched which request, whether it reached the network, how much delay it added, and turn the culprit off right there. • Search by name, URL, description or tag. • Export and import rules to share a setup — with an option to strip credentials first, so you don't hand someone your tokens by accident, and a warning when an import would collide with rules you already have. • A built-in help page explains what each rule type does and walks through the reasons a rule might not be firing. • Light and dark themes, following your system setting. PRIVACY Everything is stored locally in your browser. There is no server, no account, no analytics and no tracking. Requests shown in the DevTools panel live only in memory while DevTools is open and are never saved. Net Tinker needs broad host access because it cannot know in advance which site you will want to create a rule for. That access is used only to run the rules you configure yourself. Useful for testing APIs, simulating backend errors, exercising the loading and error states of your frontend, or debugging an integration without depending on a real environment. Available in English and Spanish.