iOS 11.4 was released today and is available as an over the air update in the Settings app. The main new features are Airplay 2, HomePod stereo pairing & Messages in iCloud.

To update, go to Settings --> General --> Software Update. Eligible devices include the iPhone 5s and later, the iPad mini 2 and later, the iPad Air and later, and the 6th-generation iPod touch.

iOS 11.4 includes AirPlay 2 multi-room audio, support for HomePod stereo pairs, and Messages in iCloud. This update also includes bug fixes and improvements.

If you want to enable Messages in iCloud you can read about it in our post How do I enable Messages in iCloud?

Apple's Release Note below:

"AirPlay 2

• Control your home audio system and AirPlay 2-enabled speakers throughout your house
• Play music at the same time on multiple AirPlay 2-enabled speakers in your house, all in sync
• Control AirPlay 2-enabled speakers from Control Center, the Lock screen, or AirPlay controls within apps on your iPhone or iPad
• Use your voice to control AirPlay 2-enabled speakers with Siri from your iPhone or iPad, HomePod, or Apple TV
• Take a call or play a game on your iPhone or iPad without interrupting playback on your AirPlay 2-enabled speakers

HomePod stereo pair

• This update supports setting up your HomePod stereo pair using your iPhone or iPad
• HomePod pair automatically senses its location in the room and balances the sound based on the speakers' locations
• Advanced beamforming provides wider soundstage than traditional stereo pair
• HomePod will automatically update to support stereo pairs, unless auto updates are disabled in the Home app 

Messages in iCloud

• Store your messages, photos, and other attachments in iCloud and free up space on your devices
• All your messages appear when you sign into a new device with the same iMessage account
• When you delete messages and conversations they are instantly removed from all your devices
• To turn on Messages in iCloud, enable Messages in iCloud settings (Settings > [your name] > iCloud)
• Your conversations continue to be end-to-end encrypted

Other improvements and fixes

• Enables teachers to assign their students reading activities in iBooks using the Schoolwork app
• Fixes an issue where certain character sequences could cause Messages to crash 
• Addresses a Messages issue that could cause some messages to appear out of order
• Addresses an issue that could prevent logging in or accessing files on Google Drive, Google Docs and Gmail in Safari
• Fixes an issue that could prevent data syncing in Health
• Fixes an issue that could prevent users from changing what apps can access Health data
• Resolves an issue that could cause an app to appear in an incorrect location on the Home screen
• Fixes an issue where CarPlay audio could become distorted
• Fixes an issue where selecting music from your iPhone could fail when playing music over Bluetooth or when connected to USB on some vehicles"