413 Payload Too Large
Meaning
The request entity is larger than the server is willing or able to process. Previously called "Request Entity Too Large."
When to Use
When the client sends a request body that is larger than the server’s limits or capabilities (e.g., uploading a file exceeding max size).
Example
Uploading a 50 MB file to a server that only accepts up to 10 MB returns 413 Payload Too Large, indicating the request size exceeds the allowed limit.
When Not to Use
Do not use if the problem is not size-related (for example, if the content is the wrong type, use 415, or if there's a semantic issue, 422). Also do not use if the server will stream or handle large payloads by design.
Source
RFC 9110