apache2 mod_rewrite stripping %2 from URLs?

Since the % is reserved for backreferences, you are can't use it like that.

Instead, change the flags to [B,r=302,NE,L] so that the "B" escapes the backreference, % in this case.

More details and examples in the docs

Interesting, thank you for the reply. It was very helpful, as back reference does seem to be the problem!

I tried your suggestion and changed the rule to add the B flag

RewriteRule ^example$ http://example.com/my%27problem [B,r=302,NE,L]

but the output was still wrong.

$ curl -I dbrks.co/example
HTTP/1.1 302 Found
Date: Tue, 09 Jan 2018 20:51:40 GMT
Server: Apache/2.4.18 (Ubuntu)
Location: http://example.com/my7problem
Connection: close
Content-Type: text/html; charset=iso-8859-1

However, when I manually escaped the the URL like so

RewriteRule ^example$ http://example.com/my\%27problem [r=302,NE,L]

then it produces the correct output.

$ curl -I dbrks.co/example
HTTP/1.1 302 Found
Date: Tue, 09 Jan 2018 20:53:50 GMT
Server: Apache/2.4.18 (Ubuntu)
Location: http://example.com/my%27problem
Connection: close
Content-Type: text/html; charset=iso-8859-1

Manually escaping the % signs is a good enough work around for me, but I wish I understood why the B flag did not have the same effect.

I don't know why the B didn't work, in theory it should have, but most probably I'm missing something from the spec.

Another alternative is to use double quotes around the url without any escaping.