URL Fragment and 302 redirects

Question

It's well known that URL fragment (the part after the #) is not sent to the server. I do wonder however how fragments work when a server redirect (via HTTP status 302 and Location: header) is involved.

My question is really two-fold:

A: If the original URL had a fragment (/original.php#foo), and a redirect is sent to /new.php, does the fragment part of the original URL simply get lost? Or does it sometimes get applied to the new URL? Will the new URL ever be /new.php#foo in this case?

B: Reguardless of the original URL, if the server redirects to a new URL with a fragment (/new.php#foo), will the fragment get "honored"? Or does the server really have no business interfering with the fragment at all - and will the browser therefore ignore it by simply going to /new.php?

Answer 1

this is an open (not specified) issue with the current HTTP specification. it is addressed in 2 issues of the IETF httpbis working group:

• #6: Fragments allowed in Location
• #43: Fragment combination / precedence during redirects

#6 allows fragments in the Location header. #43 says this:

I just tested this with various browsers.

• Firefox and Safari use the fragment in the location header.
• Opera uses the fragment from the source URI, when present, otherwise the fragment from the redirect location
• IE (8) ignores the fragment in the location URI, thus will use the fragment from the source URI, when present

Proposal:

"Note: the behavior when fragment identifiers from the original URI and the redirect need to be combined is undefined; current User Agents indeed differ on what fragment takes precedence."

[...]

It appears that IE8 does use the fragment idenfitier from Location (the behavior I saw might be limited to localhost).

Thus we seem to have consistent behavior for Safari/IE/Firefox/Chrome (just tested), in that the fragment from the Location header gets used, no matter what the original URI was.

I therefore change my proposal to document that as expected behavior.

this leads to the most browser compatible and future proof (because this issue will eventually get standardized) answer to your question:

A: fragments from original URLs get discarded.

B: fragments from the Location header are honored.