Are HTTP headers case-sensitive

Question

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

User · Answer

header  Content-type  image png    did not work with PHP 5 5 serving IE11  as in the image stream was shown as text  header  Content-Type  image png    worked  as in the image appeared as an image  Only difference is the capital  T

User · Answer

the Headers word are not case sensitive  but on the right like the Content-Type  is good practice to write it this way  because its case sensitve  like my example below  headers   headers set  Content-Type

User · Answer

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    https   tools ietf org html rfc7540 section-8 1 2

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

[http] Are HTTP headers case-sensitive?

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