Apple released a new update for iPhones and iPads on Monday with nifty features like Find My AirPods and Siri improvements, but most people won't even notice the biggest change.

As part of the iOS 10.3 update, Apple changed a basic part of how every iPhone and iPad works — its file system, or the way the computer stores data and knows where and how to find it.

With Monday's update, Apple updated iPhones and iPads to its new Apple File System, upgrading from HFS+, which was developed over 30 years ago.

It was a smart move for the future. Apple File System "is optimized for Flash/SSD storage and features strong encryption ... and improved file system fundamentals" and should help iPhones and iPads run faster and more smoothly going forward, Apple says. It may even free up GBs of storage space once you update.

But this was a risky move, too. Because a computer's file system is a fundamental part of the device, there was a chance, if something had gone wrong, that people's files could have been deleted, as Business Insider previously reported.

The good news is that 12 hours after the update went out — and was downloaded by millions — there doesn't seem to be any major problems with the transition to Apple File System. That's a big achievement for the Apple employees working on it.

If something had gone wrong, Apple would've heard about it, and it could've been bad if people actually lost their files. The one complaint is that the update takes a long time to install, and that's most likely because of the rewriting of the entire file system.

Apple could've made a big deal about this achievement. I'm sure people at Microsoft and Google, which have to push similar major updates, took notice. But instead, it pulled it off without much fanfare, and most people won't even know their iPhones have changed in a big way.