Are HTTP headers (Content-Type, &c.) case-sensitive?

Question

Perhaps I'm skimming too fast, but couldn't find this specifically documented. In my particular case, I'm wondering about the "Content-Type" header, but I'm assuming the same rules would apply to other standard headers.

Are these case sensitive, and if so: Is it Content-Type or Content-type?

Is there a proper place to reference these?

Solution 1

Case-insensitive.

Hypertext Transfer Protocol -- HTTP/1.1:

4.2 Message Headers

HTTP header fields, which include general-header (section 4.5), request-header (section 5.3), response-header (section 6.2), and entity-header (section 7.1) fields, follow the same generic format as that given in Section 3.1 of RFC 822 [9]. Each header field consists of a name followed by a colon (":") and the field value. Field names are case-insensitive.

Solution 2

Looks like the MIME type in a Content-type header value is case-insensitive, so application/PDF and application/pdf are equivalent. It does say parameter values are case-sensitive, so technically "text/html; charset=UTF-8" is not equivalent to "text/html; charset=utf-8". But that's not a good example because http://www.w3.org/TR/html4/charset.html#h-5.2.1 says "Names for character encodings are case-insensitive".

http://www.w3.org/Protocols/rfc1341/4_Content-Type.html

The type, subtype, and parameter names are not case sensitive. For example, TEXT, Text, and TeXt are all equivalent. Parameter values are normally case sensitive, but certain parameters are interpreted to be case- insensitive, depending on the intended use. (For example, multipart boundaries are case-sensitive, but the "access- type" for message/External-body is not case-sensitive.)

Comments

[Shashank Kadne]

Are field values case-insensitive too??

[Roman R.]

With rare exceptions they are too case-insensitive, however you need to check with RFC each time you are in doubts.

[Shashank Kadne]

Tell me if application/pdf and application/PDF are equal ?? I assume no..

[EricLaw]

MIME types are interpreted case-insensitively.

[Simon Tewsi]

Note that RFC 1341 has been obsoleted by RFC 2045. However the text relating to case sensitivity quoted from RFC 1341 doesn't seem to have changed in RFC 2045.

[Arend v. Reinersdorff]

@SimonTewsi I couldn't find this info in RFC 2045. It seems RFC 7231 section 3.1.1.1 is the correct one.

[Simon Tewsi]

@Arendv.Reinersdorff: See RFC 2045 section 5.1, Syntax of the Content-Type Header Field. It's on the second page of the section.

[Arend v. Reinersdorff]

@SimonTewsi Thanks for pointing it out, I missed it :-)

[Marco]

For ref on MIME types case sensitivity: tools.ietf.org/html/rfc2045#section-5.1