Open Source · Cross Platform · Any Tech Stack
Test beyond
the happy path.
Dev Proxy is an API simulator that helps you test how your app handles errors, throttling, and slow responses — without changing a single line of code.
$ devproxy
Listening on 127.0.0.1:8000...
200 GET https://api.contoso.com/users
429 GET https://api.contoso.com/data ← throttled
500 POST https://api.contoso.com/items ← server error
You test the happy path.
Your users get the rest.
APIs fail. They throttle. They respond slowly. They return unexpected data. And when they do, your app needs to handle it gracefully. But simulating these failures is hard — until now.
Resilience Testing
See how your app handles API errors.
Simulate random errors, timeouts, and failures for any API — without touching your code. Build more robust apps and never lose your customers' data.
Learn more →// Your app makes a normal API call
fetch('https://api.contoso.com/orders')
// Dev Proxy intercepts and returns
500 Internal Server Error
429 Too Many Requests
503 Service Unavailable
// Does your app handle it?
Rate Limit Simulation
Verify your app respects API limits.
Simulate rate limiting and throttling responses before they happen in production. Avoid getting blocked and deliver a smoother experience for your users.
Learn more →Retry-After: 30s
API Mocking
Mock APIs that don't exist yet.
Stand up a fully-functional CRUD API without writing a single line of server code. Design, prototype, and build your frontend in parallel with your backend.
Learn more →// No backend? No problem.
GET /products → list
POST /products → create
PUT /products/:id → update
DEL /products/:id → delete
// Zero lines of server code.
Latency Simulation
Test what happens when APIs are slow.
Add realistic latency to any API response. Make sure your loading states, timeouts, and cancellation logic work as expected.
Learn more →3,200ms
simulated response time
CI/CD Integration
Automate chaos testing in your pipeline.
Run Dev Proxy as part of your CI/CD pipeline to catch API integration issues before they reach production. Works with GitHub Actions, Azure DevOps, and more.
Learn more →# .github/workflows/test.yml
steps:
- name: Install Dev Proxy
run: bash install.sh
- name: Run tests with proxy
run: devproxy & npm test
✓ 42 passed, 0 failed
Platform Agnostic
Works with everything you use.
Dev Proxy intercepts network traffic at the system level. It works with any language, framework, and API — no SDKs, no adapters, no code changes.
.NET
Node.js
Python
Java
React
Angular
Browser
Any REST API
How does your app handle
API errors?
Find out in minutes. Dev Proxy is open source and free.