Data Transfers · Copy, Move and Sync
Does Copy overwrite files that are already at the destination?
Short answer: Identical files are skipped, changed files are replaced with the source's version, and nothing extra at the destination is deleted. Re-running the same Copy only sends what's new or changed.
Copy skips files that are already identical at the destination and replaces files whose content has changed with the source's version. It never deletes anything at the destination that isn't in the source — that's the difference from Sync (one-way).
This is also why running the same Copy again is quick: only new and changed files are sent.
If a file at the destination has the same name but you want to keep both versions, move or rename one of them before you copy.
Related: Does Sync (one-way) delete files? · Why is a re-run so fast?