Jeff Kalin Said:
"Duplicate photos never show up on iPhone 14 Plus using iOS 18.01.: There are multiple duplicates in my iPhone photos file (hundreds...). I've tried the suggested solutions in the support forum several times, and "duplicates" never appear in the utilities menu. Is there a solution to this issue?"
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These are All Cached Files —Set this Up Anew:
If you have hundreds of duplicate files, then I’d suspect these are all cached files(which is why they wouldn’t yet exist). So, I’m thinking it’d be best to backup what need be backing it all up it (i.e. enable Photos in iCloud settings). Once all is backed up, set this iPhone up anew, as if you were to sell it. Perform as instructed here, including the iCloud log out: What to do Before you Sell, Give Away, or Trade In your iPhone, iPad, or iPod touch - Apple Support