Semantics of Accept header with no value

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Semantics of Accept header with no value

danarmak (Bugzilla)
Hello,

I'm writing HTTP proxy software and there's a detail of RFC 2616 that I don't understand. Many headers (e.g. Accept-Encoding, Accept-Charset) have grammar of the form 1#(...). However, there are two headers - Accept and TE - that have grammar of the form #(...).

This difference seems to mean that an Accept header with no value is explicitly allowed and, therefore, that it has different semantics from a request with no Accept header at all. What are these semantics? As far as I can make out, a request with Accept: present but with no value should just result in a 406 Not Acceptable response. (Of course, some servers ignore the request Accept header entirely.)

Thanks in advance,

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Daniel Armak
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Re: Semantics of Accept header with no value

Julian Reschke
Hi Daniel,

you might want to follow up on httbis mailing list; see
<http://www.w3.org/html/wg/tracker/issues/118>.

That being said:

On 03.11.2010 15:31, Daniel Armak wrote:
> Hello,
>
> I'm writing HTTP proxy software and there's a detail of RFC 2616 that I
> don't understand. Many headers (e.g. Accept-Encoding, Accept-Charset)
> have grammar of the form 1#(...). However, there are two headers -
> Accept and TE - that have grammar of the form #(...).

For Accept-Encoding: this was a bug. See
<http://trac.tools.ietf.org/wg/httpbis/trac/ticket/25>.

> This difference seems to mean that an Accept header with no value is
> explicitly allowed and, therefore, that it has different semantics from
> a request with no Accept header at all. What are these semantics? As far
> as I can make out, a request with Accept: present but with no value
> should just result in a 406 Not Acceptable response. (Of course, some
> servers ignore the request Accept header entirely.)

Best regards, Julian