Where to Download iOS 18.6.1? Size difference.

[42545]

Hi,
If I try to install iOS 18.6.1 on my phone, it shows a 2GB file size, but if I try to install it from the Apple app on my PC, it shows a 8GB file size. Why is this difference? Does iOS start from scratch on the PC, but does it just add to the existing iOS on the phone? Which is better?

Best

 

[russell_314]

Hi,
If I try to install iOS 18.6.1 on my phone, it shows a 2GB file size, but if I try to install it from the Apple app on my PC, it shows a 8GB file size. Why is this difference? Does iOS start from scratch on the PC, but does it just add to the existing iOS on the phone? Which is better?

Best

My only guess is it downloads one big generic update file for all devices rather than small specific update files. This is only my guess so if someone knows the correct answer please chime in.

I haven’t connected an iPhone to a PC since my iPhone 5. I didn’t realize people still did that.

I suspect neither is better since the end result will be the same. I’d say without the PC would be easier and has one less way to fail.

 

[chrfr]

Hi,
If I try to install iOS 18.6.1 on my phone, it shows a 2GB file size, but if I try to install it from the Apple app on my PC, it shows a 8GB file size. Why is this difference? Does iOS start from scratch on the PC, but does it just add to the existing iOS on the phone? Which is better?

Best

Neither is better, the end result is the same. On the phone, Software Update only downloads the files that have changed. On your computer, the full operating system gets downloaded. The net result on your phone is identical.

 

[BigBlur]

My only guess is it downloads one big generic update file for all devices rather than small specific update files. This is only my guess so if someone knows the correct answer please chime in.

It downloads the IPSW specific for the device; there is no generic update file. You can't use the iPhone 16 Pro IPSW on an iPhone 16, for example.

 

[russell_314]

It downloads the IPSW specific for the device; there is no generic update file. You can't use the iPhone 16 Pro IPSW on an iPhone 16, for example.

So what would explain the size difference? Maybe language packs?

My thought was it had the files for all iPhones but just used the ones it needed. Of course that was just a guess.

 

[kitKAC]

Hi,
If I try to install iOS 18.6.1 on my phone, it shows a 2GB file size, but if I try to install it from the Apple app on my PC, it shows a 8GB file size. Why is this difference? Does iOS start from scratch on the PC, but does it just add to the existing iOS on the phone? Which is better?

Best

https://en.wikipedia.org/wiki/Delta_update

The Delta update is smaller and faster. You could use the full iOS IPSW to fully update and restore an iDevice.

 

[42545]

I updated my iPhone from my PC. It was a bit stressful. An 8.22 GB download was made. However, I received an error during the update. This was because the PC's internet connection was through the iPhone; the internet disconnected when the iPhone shut down. I restarted the phone, and it was in recovery mode. I was scared. I connected it to another internet connection and was able to continue the update. It took a while, but when the phone started up, everything seemed fine. Unfortunately, I saw the 18.6.2 update right afterward. However, I'll do that from my phone. However, I've been seeing the "Update requested..." message for a while now.

The Apple Devices app took a backup before the update, but it seems it didn't need to restore the backup.

 

[BigBlur]

So what would explain the size difference? Maybe language packs?

My thought was it had the files for all iPhones but just used the ones it needed. Of course that was just a guess.

Chrfr basically explained it above. The IPSW contains the entire OS; it's essentially a disk image that gets flashed to the phone. OTA updates only download the bits that changed or are different.

Just for simplicity, say an OS contains files A, B, C; and an update was made to B. The IPSW would contain A, B, C. The OTA update would only contain B since there's no need to re-download the A and C files that you already have.

The end result after the upgrade ends up being exactly the same either way. The system volume is signed, and Apple verifies it matches what they know it should be. If it doesn't match, then something went wrong and you need to try again or do a recovery. So in this regard, neither method is better since you end up with the same thing.

Personally, I'd say OTA is better though, because it gets the job done quicker.