CopyCut

CopyCut opens as a browser sidebar on any page, giving you full visibility into every API call your app makes — and full control over what gets sent and returned. - Inspect See every fetch and XHR request in real time: URL, method, status code, headers, and body. Select any request to drill into its full details. - Override Click Override on any request or response to edit it. Change the status code, headers, or body. Your changes are saved as a mock rule and applied automatically on every matching request from that point on. - Script Attach a JavaScript transform to a rule to go beyond static overrides — inject dynamic fields, simulate conditional errors, trim large lists, shift dates, or anything else your test scenario needs. - Organise Group rules into folders, enable or disable them individually, and export your mock setup as JSON to share with teammates or commit to your repo. Open it three ways: toolbar icon, right-click context menu on any page, or the DevTools panel tab. No proxy setup. No fake server. No code changes.