Please create a new ticket to track the issue unless your patch is a patch for an issue that is already ticketed. Then run the following darcs commands to generate a darcs patch file named {{{WHAT.txt}}}: {{{ darcs record darcs send -o WHAT.txt }}} And attach it to the ticket. Please use a filename like *.txt (instead of *.patch or *.diff) so that Trac will let other developers view it without first requiring them to download it first. (Trac's content-type logic maps *.patch and *.diff to some application/blahblah MIME type, which it refuses to display as HTML) If you don't have darcs or don't want to use it, just attach a normal old diff.