How to delete leftover files from aborted migrations? I recently got a new MacBook Air and used Migration Assistant (henceforth abbreviated as MA) to transfer my stuff from my old MacBook Pro. However, until MA actually worked all the way, I had to abort it and restart both machines three times. This resulted in around 50GB of wasted space in my new macbook (but no extraneous user accounts, as I read elsewhere) that I don't know how to eliminate. I assume there are some cache files that MA creates &amp; uses until the entire migration is complete. 

Where can I find these files, to delete the leftover ones from the incomplete migrations?
You could use OmniDiskSweeper (free to download and use) to search for and remove big folders. To find the problematic area fast, run it in parallel on both your macs (to see the differences) and start at the top level.

If you don't want to install additional software, you can start by running du -sg /* on both Macs, drilling down into the directories with the biggest difference and repeating du until you found the problematic files.