[ This bug is one of the recommendations in the W3C's "Common User Agent
Problems" document, URL above. One bug has been filed on each recommendation,
for deciding whether we do it and, if not, whether we should. ]
3.6 List only supported media types in an HTTP Accept header.
HTTP/1.1 [RFC2616] defines content negotiation. The client sending out
a request gives a list of media types that it is willing to accept;
the server then returns a representation of the object requested in
one of the specified formats if it is available.
When entities are embedded in a document (such as images in HTML
documents), user agents should only send Accept headers for the
formats they support.
If a user agent can render JPEG, PNG and GIF images, the list of media
types accepted should be image/jpeg, image/png, image/gif.
Wrong: User agent agents should not send an HTTP header of Accept: */*
since the server may support content types that the user agent does
not. For instance, if a server is configured so that SVG images are
preferred to PNG images, a user agent that only supports PNG, GIF, and
JPEG will receive (unsupported) SVG rather than (supported) PNG.
On the other hand, sending out a complete list of supported types is a bit of a
> On the other hand, sending out a complete list of
> supported types is a bit of a privacy problem.
Does this apply only to images, or does it apply to all supported file types?
Surely if privacy is an issue you can allow the user to disable the feature.
My personal preference would be to be able to manually edit the accept line, or
at least be able to specify q values on a per mime-type basis. Even without this
feature, sending */* as an accept header is not correct, and as a result a user
could receive an invalid file format when a valid one is available, AND not be
able to do anything about it without any control within the user-agent.
neeti: I strongly believe this bug should not be futured until there has been a
discussion on the strategy we are taking.
367 // Send */*. We're no longer chopping MIME-types for acceptance.
368 // MIME based content negotiation has died.
369 // SetHeader(nsHTTPAtoms::Accept, "image/gif,image/x-xbitmap,image/jpeg,
370 // image/pjpeg, image/png, */*");
371 SetHeader(nsHTTPAtoms::Accept, "*/*");
This comment was checked in by firstname.lastname@example.org on the 24th of March 2000,
and the SetHeader("*/*") by email@example.com on the 23rd of June 2000. What we
were sending between those times I have no idea. Nothing, I assume.
The checkin comments for neither of these checkins contain a reference to this
change. Does this change apply to all requests we send, or only those for
top-level documents? If it is all, we are definitely not in the spirit of the
RFC, and probably not the letter either...
over to networking:http
reassigning this to myself.
No reason why this shouldn't be done soon. It's a trivial fix.
let me try that again...
Trying the keywords again.
There's a patch for this in bug 58040. These are roughly the same bug, but both
have useful content, so I'm not closing either.
Gerv, I'm going to mark this as a dupe of bug 58040... so that we can focus
our attention on that bug.
*** This bug has been marked as a duplicate of 58040 ***