: URL-path with encoded question mark results in incorrect redirect when copied to target URL I have a simple RewriteRule, appending a string to some URLs: RewriteRule ^labels/([^/]+)/?$ /labels//releases/

@Ogunnowo487

You need the B flag to escape the backreference and the NE (noescape) to prevent the resulting substitution (ie. the backreference) being doubly encoded. For example:

RewriteRule ^labels/([^/]+)/?$ /labels//releases/ [B,NE,R=301,L,NC]


You will need to clear your browser cache, as the previous (erroneous) 301 will have been cached.




Why does rewriterules see the encoded %2F as an actual query string delimiter?


Slight typo there I think... you mean %3F. Yes, you end up getting 2 redirects because...


when you request /labels/label%3F%21, the RewriteRule pattern matches against the %-decoded URL-path ie. /labels/label?!. According to your rule, label?! is then copied into the substitution, resulting in a redirect to /labels/label?!/releases/ (the ?! does not get re-encoded automatically). Which is a URL-path of /labels/label and a query string of !/releases/. That's where the query string comes from.
On the redirected request, /labels/label matches your RewriteRule pattern (the query string is ignored at this stage). This time just label is copied into the substitution, to become /labels/label/releases/. And then the query string from the request is passed through to the substitution, to result in a second redirect to /labels/label/releases/?!/releases/.


The B flag escapes the captured pattern. eg. label?! is escaped to become label%3F%21.

And the NE flag prevents the % being encoded as %25 (ie. effectively doubly encoding the backreference). eg. label%3F%21 would otherwise be encoded as label%253F%2521.

Aside: mod_rewrite does not automatically encode the first ? in the substitution since it is assumed this starts the query string. However, subsequent ? will get automatically encoded. eg. Given RewriteRule ^foo$ /bar??? [R,L], a request for /foo results in a redirect to /bar?%3f%3f (note the second two ? are URL encoded, but the first one isn't).

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