Apple today reminded developers to update their Apple Watch apps to take advantage of features introduced in watchOS 4 and Apple Watch Series 3, like increased performance, new background modes for navigation and audio recording, direct connections to Core Bluetooth, and more.

Apple also announced that starting on April 1, 2018, updates to watchOS 1 apps will no longer be accepted. All updates must be native apps built with the watchOS 2 SDK or later. Newly submitted watchOS apps should be built with the watchOS 4 SDK or later.

Apple first began requiring new apps to use the watchOS 2 SDK in June of 2016, and now that will also apply to app updates that are submitted. watchOS 1 apps that are not rebuilt using watchOS 2 SDKs or later will no longer be able to be updated after the April 2018 deadline.

Apps built with the native support features that were first introduced in watchOS 2 are able to run more quickly and operate more smoothly on the Apple Watch.