When installing macOS Sequoia 15.3, iOS 18.3, or iPadOS 18.3, Apple Intelligence will be turned on automatically on compatible devices, Apple says in the developer release notes for the updates.
For users new or upgrading to iOS 18.3, Apple Intelligence will be enabled automatically during iPhone onboarding. Users will have access to Apple Intelligence features after setting up their devices. To disable Apple Intelligence, users will need to navigate to the Apple Intelligence & Siri Settings pane and turn off the Apple Intelligence toggle. This will disable Apple Intelligence features on their device
With macOS Sequoia 15.1, macOS Sequoia 15.2, iOS 18.1, and iOS 18.2, Apple Intelligence was opt-in rather than opt-out, and users who wanted the feature needed to turn it on in the Settings app. Going forward, it will be enabled by default, and Mac, iPhone, and iPad users who do not want to use the feature will need to turn it off.
macOS Sequoia 15.3 also brings Genmoji to the Mac for the first time, so Mac users will be able to create custom emoji characters after installing the update. All three new software updates add tweaks to the Notification summaries feature to make it more clear when a notification contains AI-generated information.