API Response Time Checker

What is API Response Time Checker?

An API response time checker measures the latency of HTTP requests to any endpoint by recording the time from request initiation to response completion. It typically reports DNS resolution time, TCP connection time, TLS handshake time, time to first byte (TTFB), and total response time.

How to use this calculator

1. 1Enter the full URL of the API endpoint you want to test, including protocol and path.
2. 2Set the HTTP method and add any required headers or authentication tokens.
3. 3Click Test to send the request and measure the response time.
4. 4Review the breakdown: DNS resolution, TCP connection, TLS handshake, time to first byte, and total response time.
5. 5Run multiple consecutive requests to account for cold starts, connection pooling, and caching effects.

Why this matters for founders

API performance directly impacts user experience and system reliability. Slow APIs cause timeouts, poor UX, and cascading failures in microservice architectures. Proactive latency monitoring helps founders catch performance issues before users do.