Apple released iOS 13 today, so if you've got a supported iOS device, you can go ahead and grab the OTA. For iPhones, supported devices include everything that got iOS 12 except for the iPhone 5s, iPhone 6, and iPhone 6 Plus.
Announced at WWDC this year, one of the most noticeable changes you'll find is the new dark mode. The feature showed up for macOS last year, but now it's in iOS and iPadOS, and it's consistent across the stock apps. Once you upgrade to the new version, you'll be presented with an option to switch to a dark theme, and there will also be new wallpapers that change depending on which mode you choose.
There are also redesigned Reminders and Maps apps, with smart lists on the former and an option to view 3D images of areas on the latter, similar to Google Street View. Apple Music was supposed to show you lyrics as songs are playing in Music, but that's being held back for iOS 13.1, which is currently in beta.
Photos is getting a redesign, which should separate your actual photos from screenshots, memes, and other stuff that clutters up your gallery. You'll find a new UI for editing photos, and you'll also find that you can apply all of the same effects to videos now.
Messages is getting Memoji stickers, and you'll also be able to use an image, such as a Memoji, for your profile picture, which can automatically show up for recipients. The Memoji stickers are automatically made from your Memoji.
One thing that we haven't seen in betas, since it relies on third-party apps, is a new Sign in with Apple option. Any app that lets you sign in with a third-party service - such as Facebook or Google - will be required to offer this. It lets you choose whether to provide your email address when signing up for something, and if you don't want to, Apple will give the developer a unique email address. When you cancel the service, that email address is canceled as well.
But that's not all, because watchOS 6 and tvOS 13 are now available. Both can be installed on the same devices as last year's operating systems, meaning Apple Watch Series 1 or higher, and fourth-generation Apple TV and higher.