Proxy App

API proxy and request interceptor

Proxy App is a developer tool that lets you intercept, proxy, and mock HTTP requests made by any web page — all from a convenient side panel, without installing a local server. WHAT IT DOES When you activate a workspace, Proxy App patches the fetch API of the active page. Every outgoing request is matched against your configured endpoint rules. Matched requests are forwarded to the target URL (resolving stage variables and path parameters), and the response is returned to the page transparently. Unmatched requests pass through unaffected. KEY FEATURES Proxy endpoints — Define endpoint rules with AWS API Gateway-style JSON. Requests are matched by HTTP method and path pattern, then forwarded to the configured backend URL. Stage variables (${stageVariables.name}) and path parameters ({id}) are resolved automatically. CORS bypass — Proxied requests are made from the extension background context, so cross-origin restrictions that would normally block the page do not apply. Mock responses — Mark any endpoint as a mock to return a fixed JSON response without hitting a real server. Configure the HTTP status code, response body, response headers, and an optional simulated delay. Mock database — Enable a lightweight in-memory CRUD database for a workspace. The extension automatically handles GET (list/get), POST (create), PUT/PATCH (update), and DELETE operations on your defined collections, persisting state across service worker restarts within the browser session. Request log — Every proxied and mocked request is recorded with URL, HTTP method, status code, duration, request headers, request body, response headers, and response body. Inspect individual requests in detail directly from the side panel. Multiple workspaces — Organize your proxy rules into separate workspaces. Switch between them with one click. Persistent configuration — Workspace settings and the active proxy state are saved to extension storage and restored automatically when you reopen the browser or the side panel. No local server required — Unlike desktop proxy tools, Proxy App runs entirely inside Chrome. There is nothing to install outside the browser. HOW TO USE 1. Click the Proxy App icon in the toolbar to open the side panel. 2. Create a workspace or use the default one. 3. Paste your API Gateway-style JSON configuration into the Config tab. 4. Set stage variable values in the Variables tab. 5. Enable or disable individual endpoints in the Endpoints tab. 6. Toggle the proxy ON using the switch at the top of the workspace. 7. Use the page as normal — matching requests will be proxied automatically. 8. Inspect requests in the Logs tab. USE CASES - Redirect production API calls to a local or staging backend during development. - Test frontend changes against a different API version without redeploying. - Simulate API responses with mock endpoints when the backend is not yet ready. - Debug requests in detail using the built-in request log. - Reproduce environment-specific bugs by mapping stage variables to different values. PERMISSIONS The extension requests only the permissions it needs to intercept and forward requests. See the Privacy section for a detailed explanation of each permission. Proxy App is open source. Issues and contributions are welcome.