Although the difference in DPI will not affect the quality of your picture unless you print them, it does bring some unexpected and quite messy issues when you work with pictures with different DPI.

With simple clicks, batchDPI can set all pictures in a folder to a uniform DPI you chose, no matter where they were downloaded or inputted from, or what they were edited with.
By the way, it's very interesting to find out if your favorite desktop wallpaper is originally created for Mac or PC, just check its DPI, 72dpi for Mac and 96dpi for PC. :)

Features
• Any Mac (Apple Silicon, Intel) version for macOS Big Sur
• Batch change thousands of pictures' DPI with a few simple clicks;
• Will copy (not replace) your photos to ensure the safety of your originals;
• Special destination folder first procedure protects against the overwrite of your original files;
• Toggle-able beep after each file processed;
• Progress indicator during processing;
• Destination folder will open automatically after processing;
• Supported formats: png, jpg, jpeg, other format support will be added upon your feature requests;
• New core for faster conversion
• Interface fine-tuning for dark mode
• New startup tip alert added
• All deprecated functions rewritten

Supported Operation System
• macOS 10.15 or later
• Apple Silicon or Intel Core processor

Mac App Store : https://apps.apple.com/app/batchdpi/id466331845