Shared on the Emacs Tip & Tricks thread 1. Anzu is great for previewing your query-replace as you go; just remember not to attempt it on HUGE files as the preview (or at least, result counting) gets problematic. Also remember that if you are doing a regexp replace that has side-effects (e.g. incrementing a counter), the preview itself will also do all those side effects before you run the actual replace.