19.5 Additional Features

RFC 1945 and RFC 2068 document protocol elements used by some existing HTTP implementations, but not consistently and correctly across most HTTP/1.1 applications. Implementors are advised to be aware of these features, but cannot rely upon their presence in, or interoperability with, other HTTP/1.1 applications. Some of these describe proposed experimental features, and some describe features that experimental deployment found lacking that are now addressed in the base HTTP/1.1 specification.

A number of other headers, such as Content-Disposition and Title, from SMTP and MIME are also often implemented (see RFC 2076 [37]).

19.5.1 Content-Disposition

The Content-Disposition response-header field has been proposed as a means for the origin server to suggest a default filename if the user requests that the content is saved to a file. This usage is derived from the definition of Content-Disposition in RFC 1806 [35].

content-disposition =

"Content-Disposition" ":"

disposition-type *( ";" disposition-parm )

disposition-type =

"attachment" | disp-extension-token

disposition-parm =

filename-parm | disp-extension-parm

filename-parm =

"filename" "=" quoted-string

disp-extension-token =


disp-extension-parm =

token "=" ( token | quoted-string )

An example is

Content-Disposition: attachment; filename="fname.ext"

The receiving user agent SHOULD NOT respect any directory path information present in the filename-parm parameter, which is the only parameter believed to apply to HTTP implementations at this time. The filename SHOULD be treated as a terminal component only.

If this header is used in a response with the application/octet- stream content-type, the implied suggestion is that the user agent should not display the response, but directly enter a `save response as...' dialog.

See Section 15.5 for Content-Disposition security issues.