Apple made a lot of upgrades to Reminders in iOS 13 and macOS Catalina. With new features like Smart Lists, the quick toolbar, reminder subtasks, and Siri-powered reminder notifications in Messages, the default Reminders app is better than it's ever been. But if you haven't updated your iPhone, iPad, or Mac yet to iOS 13, iPadOS 13, or macOS Catalina, upgrading Reminders to get those new features might be a tricky prospect.
It comes down to compatibility. Upgraded reminders for iOS 13 and macOS Catalina aren't compatible with earlier versions of iOS or macOS, and thus, they will no longer sync. If you rely on Reminders to track tasks across all of your devices, and you're not updating everything to the latest operating system versions right away, avoid upgrading your Reminders app on iOS 13 and macOS Catalina until updated your other devices.
Here's what you need to know about upgrading, and whether or not you should.
What "upgrading" actually means
In iOS 13, iPadOS 13, and macOS Catalina, Reminders has some new features. You can now add subtasks to your reminders to organize and plan even further. A new quick toolbar lets you add elements to your different reminders such as quickly setting a due date, location, or other pieces of information. Smart lists help automatically organize your reminders, while Siri can now suggest relevant Reminders when you're chatting with people in Messages.
When you choose to upgrade Reminders on a device with iOS 13, iPadOS 13, or macOS Catalina, these features are being enabled. If you choose not to upgrade right away, then Reminders will still work, but you'll only be able to use the old features, though you'll at least have the new look in the Reminders app.
How upgrading affects Reminders
When you first open Reminders on a device running iOS 13, iPadOS 13, or macOS Catalina, you'll be presented with a screen telling you what's new in Reminders. Additionally, you'll see two buttons at the bottom of the screen, "Upgrade Now" and "Upgrade Later." When you tap or click Upgrade Now, your Reminders in iCloud and on your devices will be upgraded to be able to use the new Reminders features like the quick toolbar and reminder subtasks. You only need to tap or click this button once, and Reminders will be upgraded across all of your updated devices signed into your iCloud account.
When you upgrade, your current reminders will stay as they are. They will, though, be compatible with the new iOS 13/macOS Catalina Reminders features like subtasks. Your lists will also seem to be as they were, but with the new Reminders framework, you can place multiple lists into a single group for easier organization. You'll also see the new smart lists: Today, Scheduled, All, and Flagged.
Once upgraded, though, your reminders will no longer sync to devices that aren't running iOS 13, iPadOS 13, or macOS Catalina. If you still have a device on macOS Mojave or iOS 12, you'll be out of luck. It's also worth keeping in mind that this will affect any shared reminders that you have. If the person or people you share reminders with doesn't upgrade their devices and you do, your shared reminders together will no longer work.
This is why the Upgrade Later button exists. If you have the newer operating systems installed only on some of your devices and you still want to use Reminders on everything, or you share reminders with someone who hasn't updated their devices to the new operating systems yet, tap Upgrade Later and you'll still be able to use Reminders as you always have up until now in a kind of compatibility mode.
You won't be able to take advantage of most of the new features, but you'll at least be able to sync reminders to all of your devices and share reminders with people that haven't upgraded.
Should you upgrade Reminders?
If you haven't installed iOS 13, iPadOS 13, and macOS Catalina on all of the devices with which you use Reminders, and you rely on Reminders for your to-dos, then no, don't upgrade just yet. Likewise, don't upgrade even if you have updated everything if you have shared reminders with someone who hasn't upgraded.
But if you and everyone with whom you need to share reminders have updated their devices, then upgrade away. Your existing reminders will be where they always were and you get a new set of capabilities that make the app better than ever.
If you've got any further questions about upgrading Reminders, let us know in the comments.