In a number of Apple Mac apps (including Preview, Pages, and Keynote), macOS added the quiet feature of retaining older versions of document you modify. This versioning feature doesn’t require Time Machine, even though it looks a lot like that feature and service. You don’t even have to enable it—it just works in apps that support it. You can access past versions via File > Revert To > Browse All Versions.
These apps store a version every hour while you’re working on it, or more frequently if major changes are made. There’s no hard-and-fast rule about how far back these versions are stored. They tend to take up fairly little space, because Apple relies on storing just the differences between two files, which for most editing involves very little overhead.
But some folks who perform a lot of manipulation to files, particularly images, want to get rid of older copies so as not to fill sometimes scarce storage with versions they don’t need. There’s slightly convoluted way to delete these snapshots.
With document in question open, choose File > Revert To > Browse All Versions.
From the browsing window that appears, navigate through time to the first version you want to delete, selecting it in the right-hand side of the view.
Move your cursor up to the top of the screen for a moment until the menus reveal themselves.
Choose File > Revert To > Delete This Version and confirm the deletion.
Repeat steps 2 to 4 for each older version you want to get rid of, and steps 1 to 4 for every document you want to purge of past edits.
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