As far as I can tell, iOS does some really strange things when it comes to compressing the media in your Photos app.

It seems that any time you use the "share" sheet, it's compressing your photos slightly, even when using AirDrop. Comparing a photo transferred via Airdrop to one transferred via copy/pasting in Windows Explorer, there's a fairly significant file size difference (2.98MB vs 3.75MB). At first I thought this may be due to some sort of lossless compression, but then I compared some videos, and the actual bitrate on the video streams differed when transferred via USB vs any other app or Airdrop (12mbps vs 14mbps).

~~Going to the settings app and changing the "Transfer to PC or Mac" setting to "Keep Originals" under the photos section makes no difference.~~

EDIT: It absolutely does, see my answer below.

As far as I can tell, transferring via USB to a Windows PC is the only way to do it. But...this can't be the only way, right? There should be a proper way to do it within the Apple ecosystem. But yet, MacOS won't even entertain the idea of letting you transfer photos via USB lightning cable as long as you have iCloud photos enabled. And iCloud photos' option of downloading the "unmodified original" from the web app is a complete misnomer, as a 3.75MB photo comes down as 1.95MB, and full HD videos actually come down in 720p.

Anyone with any insight as to how iOS's compression system works would really help me out here. Thanks in advance.

  • 1
    What are you asking? The proper way to transfer? Or the compression algorithm?
    – Solar Mike
    Nov 30, 2021 at 7:45
  • @SolarMike I'm asking how to transfer the original files without any lossy compression. Nov 30, 2021 at 19:02
  • 1
    I should've mentioned in my original post, transferring to a Windows PC is EXTREMELY buggy, and has been that way for as long as I remember (I'm having the same issues with my iPhone 12 that I was with my iPhone 4S 10 years ago) Nov 30, 2021 at 19:05
  • I find doing anything on Windows tends to be buggy - why I run mac…
    – Solar Mike
    Nov 30, 2021 at 19:21
  • 1
    If mac would let me transfer photos over USB, I'd happily use it, but it doesn't, so I can't... Nov 30, 2021 at 20:20

2 Answers 2


Alright, it seems I've made a bit of a deduction mistake - turns out changing "Automatic" to "Keep Originals" under Photos in the Settings app makes all the difference. Depending on which option is checked, the files will show up differently in Windows Explorer. The "Transfer to PC or Mac" section of the Photos menu of the Settings app.

"Automatic" makes them show up as .jpg files. "Keep Originals" makes the photos show up as HEIC files. That's the reason for the size difference (.heic files are much smaller).


There is a way to transfer photo files from the iOS device to your MacOS device by way of running the Image Capture app from the MacOS device. This application has import by selection or Import All functionality. It copies all the metadata for the image files as well including the creation and modification dates of the original file present on the iOS device.

Image Capture screenshot

The last section in this support page covers a bit about the compression

Importing this media via USB

When you import HEIF or HEVC media from an attached iOS device to Photos, Image Capture, or a PC, the media might be converted to JPEG or H.264.

You can change this import behavior in iOS 11 or later. Go to Settings > Photos. In the TRANSFER TO MAC OR PC section, tap Keep Originals to prevent the media from being converted to JPEG or H.264 when importing.


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