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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?

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up vote 23 down vote accepted


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.

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Are field values case-insensitive too?? –  Shashank Kadne Feb 22 '12 at 11:15
With rare exceptions they are too case-insensitive, however you need to check with RFC each time you are in doubts. –  Roman R. Feb 22 '12 at 11:22
Tell me if application/pdf and application/PDF are equal ?? I assume no.. –  Shashank Kadne Feb 22 '12 at 11:25
MIME types are interpreted case-insensitively. –  EricLaw Dec 13 '12 at 16:17
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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".


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.)

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