What is the error ERR_HTTP2_PROTOCOL_ERROR and how to fix it

The ERR_HTTP2_PROTOCOL_ERROR is an error that occurs in HTTP/2, the second major version of the HTTP network protocol. This error typically indicates that there was a protocol violation or an issue with the HTTP/2 communication between the client (e.g., a web browser) and the server. The error is often encountered when using modern web browsers or applications that rely on HTTP/2 for faster and more efficient communication.

Common Causes of ERR_HTTP2_PROTOCOL_ERROR

• Server Misconfiguration: The server might not be properly configured to handle HTTP/2 requests.
• Incompatible Middleware or Proxy: A proxy, load balancer, or middleware might not fully support HTTP/2 or could be misconfigured.
• Corrupted Cache or Cookies: Browser cache or cookies might be corrupted, causing issues with HTTP/2 communication.
• Network Issues: Intermittent network problems or packet loss could disrupt the HTTP/2 connection.
• Browser Bugs: The browser might have a bug or incompatibility with the server’s HTTP/2 implementation.
• SSL/TLS Issues: HTTP/2 requires HTTPS, and problems with SSL/TLS certificates or configuration can cause this error.

How to Fix ERR_HTTP2_PROTOCOL_ERROR

1. Clear Browser Cache and Cookies

Corrupted cache or cookies can cause HTTP/2 issues. Clear your browser’s cache and cookies and try reloading the page.

Steps:

• Open your browser settings.
• Navigate to the privacy or history section.
• Clear cache and cookies.

2. Check Server Configuration

Ensure your server is properly configured to support HTTP/2.

For example, if you’re using Nginx, verify that the http2 directive is enabled in your configuration file:

listen 443 ssl http2;

For Apache, ensure the mod_http2 module is enabled:

sudo a2enmod http2
sudo systemctl restart apache2

3. Disable HTTP/2 Temporarily

If the issue persists, try disabling HTTP/2 on the server and fall back to HTTP/1.1 to see if the problem is resolved.

For Nginx:

listen 443 ssl; # Remove http2

For Apache:

sudo a2dismod http2
sudo systemctl restart apache2

4. Check for Proxy or Middleware Issues

If you’re using a proxy (e.g., Cloudflare, NGINX, or HAProxy), ensure it supports HTTP/2 and is configured correctly. Temporarily bypass the proxy to see if the issue is related to it.

5. Verify SSL/TLS Configuration

Ensure your SSL/TLS certificate is valid and properly configured. Use tools like SSL Labs’ SSL Test to check for issues.

6. Update Your Browser

Ensure your browser is up to date, as outdated versions might have bugs or incompatibilities with HTTP/2.

7. Check Network Connectivity

Test your network connection for stability. Use tools like ping or traceroute to check for packet loss or latency issues.

8. Inspect Server Logs

Check your server logs for any errors or warnings related to HTTP/2. This can provide more insight into the root cause.

9. Disable Browser Extensions

Some browser extensions might interfere with HTTP/2 communication. Disable extensions and try again.

10. Contact Your Hosting Provider

If you’re using a shared hosting service or a managed server, contact your hosting provider to ensure their infrastructure supports HTTP/2 correctly.

Debugging Tools

• Use browser developer tools (e.g., Chrome DevTools) to inspect network requests and identify where the error occurs.
• Use command-line tools like curl with the --http2 flag to test HTTP/2 connectivity:

  curl -I --http2 https://yourwebsite.com

By following these steps, you should be able to identify and resolve the ERR_HTTP2_PROTOCOL_ERROR. If the issue persists, consider consulting with a server administrator or web developer for further assistance.