Why does MacOS use swap even when memory is not fully used?

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Hmm .... My guess is that you think this subreddit is about Macs, but it's not, it's about [the text editor Emacs](https://en.wikipedia.org/wiki/GNU_Emacs). (The first 'Emacs' editor was created in 1976, the first Macintosh came out in 1984.) If my guess is correct, perhaps try posting in r/MacOS.