HTTP2.Pro — Test Client and Server HTTP/2 Protocol Support API (No Key)

TL;DR

HTTP2.Pro provides a simple endpoint to test whether your HTTP client or a remote server supports HTTP/2. Hit the /api/v1/check endpoint and it returns your connection's HTTP version, ALPN protocol negotiation details, TLS cipher information, and server push capabilities. Useful for debugging CDN configurations, verifying server setups, or testing if your HTTP library is negotiating H2 correctly.

Quick start: https://http2.pro/api/v1/check

No API key needed — just make a request!

Check if you're connecting via HTTP/2: https://http2.pro/api/v1/check

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How to Use This API

1. Check HTTP/2 Support

Simply make a GET request — the response tells you everything about your connection:

https://http2.pro/api/v1/check

Returns JSON: protocol (http/1.1 or h2), alpn (yes/no), cipher_suite, tls_version, http2_push (if applicable), and user_agent.

2. JavaScript — Test Your Connection

fetch('https://http2.pro/api/v1/check')
  .then(res => res.json())
  .then(data => {
    console.log('Your connection uses:', data.protocol);
    if (data.protocol === 'h2') {
      console.log('✓ HTTP/2 supported!');
    } else {
      console.log('✗ Using HTTP/1.1');
    }
    console.log('TLS:', data.tls_version || 'N/A');
  });

3. Python — Verify CDN Serving H2

import requests

resp = requests.get('https://http2.pro/api/v1/check')
check = resp.json()
print(f"Protocol: {check['protocol']}")
print(f"ALPN: {check['alpn']}")
print(f"Cipher: {check.get('cipher_suite', 'unknown')}")
if check['protocol'] == 'h2':
    print("✓ Your client is using HTTP/2")
else:
    print("✗ Falling back to HTTP/1.1")

Frequently Asked Questions

What is HTTP/2 and why does it matter?: HTTP/2 (h2) is a major revision of the HTTP protocol that enables multiplexed streams, header compression (HPACK), and server push — resulting in faster page loads compared to HTTP/1.1.
What information does the check endpoint return?: It returns: protocol (h2 or http/1.1), whether ALPN was negotiated, TLS version, cipher suite, HTTP/2 push capability, and your request headers.
Do I need an API key?: No. HTTP2.Pro is completely free with no authentication required.
Can I test a specific remote server?: The current endpoint tests your connection to http2.pro. For testing arbitrary servers, you would need to use a tool like curl or a browser's developer tools.
Does the API support other HTTP methods?: The check endpoint accepts GET requests. It primarily inspects the connection properties rather than method-specific behavior.
Are there rate limits?: No published rate limits. The service is intended for development testing and debugging.

API Details

API URL: https://http2.pro/api/v1/check
Documentation: http2.pro/doc/api
Category: Development
Authentication: Not Required
Geographic Coverage: Global

What You Can Build

DevOps dashboard that verifies HTTP/2 support across your infrastructure
CDN comparison tool that tests which providers support HTTP/2 from different regions
CI/CD pipeline check that ensures your web server config enables h2 correctly
Debugging helper for HTTP library issues — confirm your client negotiates HTTP/2
Educational tool demonstrating HTTP/2 vs HTTP/1.1 protocol differences