Open the Google Photos app
Tap your profile picture or initial
Tap Photos settings
Tap Backup
Turn off Backup
On iPhone, you can also remove Google Photos access in Settings if needed
On Android, you can also disable app permissions if needed
To stop syncing a specific device, repeat the steps on that device
To remove already backed-up photos from Google Photos, delete them from the Google Photos library
To stop Google Photos from syncing with Google Drive, open Google Photos settings and turn off Google Drive sync if available