HTTP 421 Misdirected Request — TLS/HTTP2 Routing Error

HTTP 421 Misdirected Request means the request was directed at a server that cannot produce a response, often due to HTTP/2 connection coalescing issues. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: Introduced in HTTP/2 specification (RFC 7540) for connection multiplexing issues. HTTP/2 connection coalescing allows reusing connections for different hostnames on the same IP. 421 occurs when the server cannot serve the requested hostname on the reused connection. The TLS certificate may not cover the requested hostname. Client should retry on a new, dedicated connection to the correct server. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: HTTP/2 connection coalescing sending request to wrong virtual host. TLS certificate does not cover the requested domain name. CDN routing request to a server that does not host the requested domain. Load balancer misconfiguration with shared IP addresses. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Retry the request — client should open a new connection and try again. Verify TLS certificate covers the domain using openssl s_client -connect host:443. Check CDN configuration to ensure correct origin mapping for each domain. If using shared hosting, verify SNI is properly configured. Disable HTTP/2 connection coalescing as a temporary workaround. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our HTTP Status Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.