HTTP 417 Expectation Failed vs 421 Misdirected Request
Both HTTP 417 (Expectation Failed) and 421 (Misdirected Request) belong to the 4xx Client Error category. 417 indicates that the server cannot meet the requirements of the Expect header. Meanwhile, 421 means that the request was directed at a server that is unable to produce a response for the combination of scheme and authority in the URI.
Description
The server cannot meet the requirements of the Expect header.
When You See It
When the server doesn't support Expect: 100-continue.
How to Fix
Remove the Expect header from your request.
Description
The request was directed at a server that is unable to produce a response for the combination of scheme and authority in the URI.
When You See It
With HTTP/2 when a connection is reused for a domain the certificate doesn't cover.
How to Fix
Retry the request on a new connection.
Key Differences
HTTP 417: The server cannot meet the requirements of the Expect header.
HTTP 421: The request was directed at a server that is unable to produce a response for the combination of scheme and authority in the URI.
You encounter 417 when when the server doesn't support Expect: 100-continue.
You encounter 421 when with HTTP/2 when a connection is reused for a domain the certificate doesn't cover.
When to Use Which
For 417 (Expectation Failed): Remove the Expect header from your request. For 421 (Misdirected Request): Retry the request on a new connection.