Troubleshoot protocol issues

This guide covers common HTTP/2 and HTTP/3 issues, including origin incompatibility, multiplexing errors, and browser errors, with steps to diagnose and resolve them.

H2 to Origin - Origin incompatibility

• The origin's max_concurrent_streams is negotiated during the handshake process.
• If a GOAWAY(0) is received, it is likely due to a server restart or another reason causing the server to refuse new streams.
• For more information, refer to RFC 9113 - SETTINGS_MAX_CONCURRENT_STREAMS ↗.

H2 Multiplexing - Origin incompatibility/issues

• Multiplexing issues can arise due to incorrect server configurations.
• Use netlogs ↗ to identify SETTINGS_MAX_CONCURRENT_STREAMS violations or unexpected GOAWAY frames.
• For more information, refer to Stream Concurrency Issues ↗.

Generic browser errors

Common browser errors include:

• ERR_HTTP2_PROTOCOL_ERROR
• ERR_HTTP3_PROTOCOL_ERROR
• ERR_QUIC_PROTOCOL_ERROR

These errors do not necessarily indicate a protocol-level issue. Follow these steps:

1. Attempt reproduction using HTTP/1.1.
2. If the issue persists in HTTP/1.1, address the underlying error before testing HTTP/2 or HTTP/3.
3. If the issue does not persist, analyze netlogs for HTTP/2 or HTTP/3-specific issues.

For more information, refer to Chromium URL Request Header ↗.