What is ERR_SPDY_PROTOCOL_ERROR?

The ERR_SPDY_PROTOCOL_ERROR occurs in Chrome when there is an issue with the SPDY or HTTP/2 protocol. This error can appear while trying to load a website, even for well-known domains. It typically stems from browser or server misconfigurations.

Understanding SPDY Protocol

SPDY was a protocol developed by Google to improve upon HTTP/1.1 by speeding up page load times and enhancing security. It evolved into the HTTP/2 standard, which is now widely adopted. Chrome supports both SPDY and HTTP/2, but issues with the protocol implementation can trigger this error.

When a browser supports SPDY/HTTP/2, it sends headers to indicate compatibility. The server responds using the appropriate protocol, but if there’s a mismatch, the connection defaults to HTTP/1.1 or fails, resulting in an error.

Common Causes and Fixes for ERR_SPDY_PROTOCOL_ERROR

Below are the most common causes of this error and their corresponding solutions:

1. Outdated Chrome Browser

An outdated Chrome browser may not fully support SPDY/HTTP/2. To fix this:

1. Open Chrome and go to Settings > About Chrome.
2. Update Chrome to the latest version and restart the browser.

2. Outdated Cache and Cookies

If a website has transitioned to HTTPS, old HTTP cookies may cause the error. To clear the cache and cookies:

1. Click the three-dot menu in Chrome, select Settings, and go to Privacy and Security > Clear browsing data.
2. Choose All time for the time range, check Cookies and Cached images, and click Clear data.
3. Restart the browser.

3. Firewall Configuration

Your firewall may block Chrome or specific ports. To resolve this:

• On Windows: Go to Control Panel > Windows Firewall > Allowed apps, and ensure Chrome is checked.
• On MacOS: Check your firewall settings under System Preferences > Security & Privacy > Firewall.

4. Flush Socket Pools

Flushing socket pools can resolve connection issues:

1. Enter chrome://net-internals/#sockets in the address bar.
2. Click Flush socket pools.

5. Renew IP Address

Renewing your IP address can help resolve network-related issues:

Windows

1. Open the Command Prompt as an administrator.
2. Run the following commands:
   

   
   ipconfig /flushdns
   ipconfig /release
   ipconfig /renew
           

MacOS

1. Go to Network Settings, select your connection, click Advanced, and navigate to the TCP/IP tab.
2. Click Renew DHCP Lease.

6. Use Incognito Mode

Open an incognito window to bypass cookies and extensions that might cause conflicts:

• On Windows: Press Shift + Ctrl + N.
• On MacOS: Press Shift + Command + N.

7. Use Chrome Cleanup Tool

Chrome's cleanup tool can identify and remove harmful software:

1. Go to Settings > Advanced > Clean up computer.
2. Click Find to scan for malware and Remove to delete it.

Additional Steps to Resolve ERR_SPDY_PROTOCOL_ERROR

If the above methods don’t resolve the issue, try these advanced solutions:

1. Temporarily Disable VergeCloud

Turn off the cloud icon in your VergeCloud panel to bypass the CDN and test DNS resolution directly.

2. Check Content-Length Header

Ensure the Content-Length header matches the actual size of the sent body to avoid conflicts.

3. Verify Response Headers

Check that your server’s response headers comply with HTTP standards. Refer to your web server’s documentation (e.g., Apache or Nginx) for guidance.

4. Update Web Server

An outdated web server may not support SPDY/HTTP/2. Ensure your server is running the latest version to maintain compatibility.

Considerations

• Always update Chrome to the latest version to avoid protocol-related issues.
• Regularly clear your browser’s cache and cookies, especially after making significant changes to your site.
• Ensure your web server supports the latest HTTP/2 protocol for compatibility with modern browsers.
• Use VergeCloud’s panel to verify DNS configurations and temporarily disable the Cloud Icon if needed.
• Test your server using tools like MTR or traceroute for deeper diagnostics.