API Latency Tester
Measure response time for one or more API endpoints. Requests run sequentially from your browser with precise timing, and every result is color-coded so slow endpoints stand out immediately.
How to use
- Paste one or more full endpoint URLs, one per line. Use the sample button to try public test endpoints.
- Choose GET or POST. For POST you can add a custom header and a request body, which is sent to every URL.
- Click "Run latency test" and watch the results table fill in as each request finishes.
- Compare the latency badge and the summary chips to find slow or failing endpoints.
Note: some endpoints may fail with the message "request blocked by browser CORS policy" — that means the target server does not permit browser-based requests, and no client-side tool can bypass it. Run tests over HTTPS for reliable timing.
Tips
- Test each endpoint a few times — first-request timing is often slower because of DNS and connection setup.
- A red result over 1 second on a simple endpoint usually means the server is slow, not your connection.
- For POST testing, set Content-Type to application/json and paste valid JSON in the body box.