Why does Google Takeout have duplicate photos?

Your Takeout download is much bigger than your Google Photos library, and the same photo turns up in several folders. That's how Takeout handles albums.

Where the copies come from

Year folders. Every photo appears once in a folder like Photos from 2019.
Album folders. Each album is a separate folder containing its own copy of every photo in it. A photo in three albums is stored four times.
Edited copies. If you edited a photo in Google Photos you may also get IMG_1234-edited.jpg next to the original.

Removing them without losing your albums

Deleting the album folders saves space but throws away which photos were in which album. A safer way is to keep one copy of each photo and save the album list separately.

Takeout Photo Fixer finds exact duplicates (same size, same content), keeps the copy from the year folder, and writes an albums.csv file listing every album and its photos. Edited copies are kept, because they're different pictures. It also fixes the wrong dates while it's at it.

See how many duplicates you have: it's free