The Deprecation HTTP response header field is used to signal to consumers of a resource (in the sense of URI) that the resource will be or has been deprecated. Additionally, the deprecation link relation can be used to link to a resource that provides additional information about planned or existing deprecation, and possibly ways in which clients can best manage deprecation.
I don’t really get the purpose of a header like this, who is supposed to check it? It’s not like developers casually check the headers returned by an API every week.
Write them a mail if you see deprecated functions being used by a certain API key, probably much more likely to reach somebody that way.
Also, TIL that the IETF deprecated the
X-
prefix more than 10 years ago. Seems like that one didn’t pan out.Can you elaborate on that? The X- prefix is supposedly only a recommendation, and intended to be used in non-standard, custom, ah-hoc request headers to avoid naming conflicts.
Taken from https://datatracker.ietf.org/doc/html/rfc6648
I still work on software that extendively uses X- headers.
The RFC you linked recommends that no new
X-
prefixed headers should be used.The paragraph you quoted does not say you should use the
X-
prefix, only comments on how it was used.See section 3 for the creation of new parameters: https://datatracker.ietf.org/doc/html/rfc6648#section-3
I wouldn’t worry too much about it. The reason they give is mostly that it is annoying if a
X-
header suddenly becomes standardized and you end up having to supportX-Something
andSomething
. Most likely a non-issue with real custom headers.It makes sense to include so it’s obvious in the readable HTTP request response. We use readable URLs and header names for the same purpose: So it is inspectable and understandable from that text format. You may leave deprecation information out, but then you’re missing part of the resource description that you’re addressing with the URL/URI.
Given a defined header it also allows you to add tooling and automation. There’s no need for manual reading.
You can simply log this response. Then developers know to replace that call in the next version. If you have unit tests that look for this then you can be sure that your next version is not using any deprecated API calls.
We don’t have many unit tests that test against live APIs, most use mock APIs for testing.
The only use for this header would be if somebody sees it during development, at which point it would already be in the documentation or if you explicitly add a feature to look if the header is present. Which I don’t see happening any time soon since we get mailed about deprecations as well.