knock

Intercept, modify, or pause fetch/XHR in any page. Rule-based response overrides, cookie injection, and in-page live editing.

knock is a Chrome DevTools extension for frontend developers. It intercepts the current tab's fetch and XMLHttpRequest traffic so you can record every request, define rule pipelines, modify outgoing requests, synthesize responses, inject cookies, or pause either side and finish it from an in-page floating editor. Everything runs locally on your machine. No data leaves the browser. WHAT YOU CAN DO • Record every fetch and XHR call with method, URL, captured time, response status, headers, and body — Request and Response detail panels show the post-modify state, matching what Chrome's Network tab logged. • Build rule pipelines. Every matched rule runs in list order (Express middleware style), so later rules see earlier rules' output. Drag to reorder; a #N badge shows each rule's position. • Modify outgoing requests: headers, query params, body, cookies. Each field has an Original / Override / Replace mode so you choose how the rule blends with the page's value. • Synthesize responses: status, headers, body, delay, and persistent Set-Cookies. • Pause and edit live. A draggable, resizable in-page floating editor lets you craft the request (or response) by hand and accept it. Multiple pause windows can stack. • Inject cookies the right way. The Cookies and Set-Cookies sections route through chrome.cookies (request-scoped and restored after settle for outgoing; persistent for response-side, mirroring real Set-Cookie). The pause editor pre-populates with the live cookie jar so you edit real state. • Scenarios with domain allowlists. Save named rule bundles and pick one per tab; the scenario auto-disables when the tab URL isn't in its allowlist — so a "production" scenario won't accidentally fire on localhost. • Export / import rules as JSON. • Master on/off toggle in the panel header and toolbar popup detaches the interceptors entirely.