Can a 204 response have a body?

No. The specification forbids it, and sending one causes clients and proxies to mis-frame the response or hang. Watch for frameworks that serialise a return value automatically.

204 or 200 for a successful DELETE?

204 when there is nothing useful to return, which is the usual case. 200 with a body is fine if you have something worth sending - a summary of what was removed, for instance.

What should a DELETE return if the resource was already gone?

Either 204 (treating delete as idempotent, which is the common and friendlier choice) or 404. Pick one and document it - clients writing retry logic need to know.

204 No Content

The request succeeded and there is deliberately no response body.

Class 2xx · Success
Retry Do not retry

What 204 means

204 means success with nothing to say. It is the natural response to a DELETE that removed something, a PUT or PATCH where the client already knows the resulting state, and any action endpoint with no meaningful result to return.

A 204 response must not include a body. This is a hard rule, not a convention, and violating it causes real problems: some clients and intermediaries mis-frame the response or wait for content that never arrives. Frameworks that automatically serialise a return value can produce a 204 with a body without you noticing.

Content-Length must also be absent rather than 0 in a strict reading, though in practice most stacks handle either.

Should a client retry?

Succeeded. A retried DELETE that returns 204 again is fine - DELETE is idempotent.

FAQ

Can a 204 response have a body?: No. The specification forbids it, and sending one causes clients and proxies to mis-frame the response or hang. Watch for frameworks that serialise a return value automatically.
204 or 200 for a successful DELETE?: 204 when there is nothing useful to return, which is the usual case. 200 with a body is fine if you have something worth sending - a summary of what was removed, for instance.
What should a DELETE return if the resource was already gone?: Either 204 (treating delete as idempotent, which is the common and friendlier choice) or 404. Pick one and document it - clients writing retry logic need to know.

Often confused with

200 OK The request succeeded and the response carries the result.
404 Not Found The server has no resource at that URL.