In a blog post I use the following PHP to set the content-type of a response:
header('content-type: application/json; charset=utf-8');
I just got a comment on that post saying that content-type needs to be capitalized, Content-type. Is this correct? It seems to work for me with all lower-case, and I assumed the HTTP headers were case-insensitive. Or does it just work because browsers are nice?
Header names are not case sensitive.
From RFC 2616 - "Hypertext Transfer Protocol -- HTTP/1.1", Section 4.2, "Message Headers":
Each header field consists of a name followed by a colon (":") and the field value. Field names are case-insensitive.
The updating RFC 7230 does not list any changes from RFC 2616 at this part.
HTTP header names are case-insensitive, according to RFC 2616:
4.2:
Each header field consists of a name followed by a colon (":") and the field value. Field names are case-insensitive.
(Field values may or may not be case-sensitive.)
If you trust the major browsers to abide by this, you're all set.
BTW, unlike most of HTTP, methods (verbs) are case sensitive:
5.1.1 Method
The Method token indicates the method to be performed on the
resource identified by the Request-URI. The method is case-sensitive.Method = "OPTIONS" ; Section 9.2 | "GET" ; Section 9.3 | "HEAD" ; Section 9.4 | "POST" ; Section 9.5 | "PUT" ; Section 9.6 | "DELETE" ; Section 9.7 | "TRACE" ; Section 9.8 | "CONNECT" ; Section 9.9 | extension-method extension-method = token
tldr; both HTTP/1.1 and HTTP/2 headers are case-insensitive.
According to RFC 7230 (HTTP/1.1):
Each header field consists of a case-insensitive field name followed by a colon (":"), optional leading whitespace, the field value, and optional trailing whitespace.
https://tools.ietf.org/html/rfc7230#section-3.2
Also, RFC 7540 (HTTP/2):
Just as in HTTP/1.x, header field names are strings of ASCII
characters that are compared in a case-insensitive fashion.
They are not case sensitive. In fact NodeJS web server explicitly converts them to lower-case, before making them available in the request object.
It's important to note here that all headers are represented in lower-case only, regardless of how the client actually sent them. This simplifies the task of parsing headers for whatever purpose.
The RFC for HTTP (as cited above) dictates that the headers are case-insensitive, however you will find that with certain browsers (I'm looking at you, IE) that capitalizing each of the words tends to be best:
Location: http://stackoverflow.com
Content-Type: text/plain
vs
location: http://stackoverflow.com
content-type: text/plain
This isn't "HTTP" standard, but just another one of the browser quirks, we as developers, have to think about.
officially, headers are case insensitive, however, it is common practice to capitalize the first letter of every word.
but, because it is common practice, certain programs like IE assume the headers are capitalized.
so while the docs say the are case insensitive, bad programmers have basically changed the docs.
I have used code as below:
reqObj['headers'] = new Headers({
CSRF: ABCD-DEFG..,
});
I could see it getting converted to lowercase ('csrf'). Will revisit, and update with further findings. However, as it is being done by the constructor, I assume it should be working. Hence also, Headers seem to be case-insensitive.
