If you're running low on your 15GB Google Drive storage allotment or dealing with a slow internet connection, select Express to back up media at the lowest resolution. The media uploads offer a respectable quality print up to 24-by-16 inches. To save storage space, it compresses photos to 16 megapixels and videos to a high quality. Storage saver stores more media files at a slightly reduced quality. Storage saver is a nice balance between Original quality and the Express option. It's also suitable for large prints without quality loss. If you plan to shoot a lot of photos in full resolution (48MP, 64MP, 108MP, or 200MP), use the Original quality option. The option backs up your photos and videos in full resolution. Google scrapped the add-on in June 2021, though people who own a Pixel 5 smartphone or an earlier model are still eligible for unlimited storage for photos and videos.

Google used to offer unlimited storage for original-quality uploads to Pixel users.

If you're unsure of the option you should pick, here's a quick rundown of Google Photos various image quality options.

Google photos backup iphone