It’s critical to keep your operating system and applications up to date. Turn on automatic updates for your operating system and App Store apps, and restart your computer frequently to allow other apps to check for updates.
Recommended versions of Apple operating systems:
macOS: Monterey 12.3.1 or newer

If your Mac supports it, you should be running macOS Monterey 12.3.1 or newer. If you have an older Mac, you should be running either macOS Big Sur 11.6.5 or macOS Catalina 10.15.7 with all Security Updates installed.
To see what version of macOS you have, click on the Apple menu and choose “About This Mac”.
How to update macOS (apple.com)
macOS Monterey is compatible with these computers (apple.com)
What’s new in the updates for macOS Monterey

iOS & iPadOS: 15.5 or newer


Your iPhone and iPad should be running the latest version of iOS & iPadOS, 15.5. If your device is too old to be updated, it should be replaced.
Update your iPhone, iPad, or iPod touch (apple.com)
iPhone models compatible with iOS 15 (apple.com)
iPad models compatible with iPadOS 15 (apple.com)
About iOS 15 Updates

Other updates
Is my browser out of date? (whatismybrowser.com)
How to update your Apple TV (apple.com)
How to update your Apple Watch (apple.com)
Apple security updates (apple.com)
(Featured image “Upgrade” by Ged Carroll licensed under CC BY 2.0)