Apple today released iOS 15.4 and iPadOS 15.4, the fourth major updates to the iOS and iPadOS 15 operating systems that were released in September 2021. iOS and iPadOS 15.4 come a month after the launch of iOS 15.3.1 and iPadOS 15.3.1.

The iOS 15.4 and iPadOS 15.4 updates can be downloaded for free and the software is available on all eligible devices over-the-air in the Settings app. To access the new software, go to Settings > General > Software Update.

iOS 15.4 adds an option to use Face ID while wearing a mask, which works just like normal ‌Face ID‌ but scans the areas around your eyes for authentication. iPadOS 15.4 introduces Universal Control, allowing multiple Macs and iPads to be controlled with the same mouse/trackpad and keyboard.

The updates also add 37 new emoji characters and they lay the groundwork for the new "Tap to Pay on iPhone" feature that allows NFC-compatible iPhones to accept payments through Apple Pay. There are also updates to add custom domains to iCloud Mail right on device, Siri enhancements, new Emergency SOS features, and tons more. Apple's full release notes for the update are below:

Face ID
- Face ID while wearing a mask option on iPhone 12 and newer
- Apple Pay and password autofill in apps and Safari can be used with Face ID while wearing a mask

Emoji
- New emoji including faces, hand gestures, and household objects are now available in emoji keyboard
- Handshake emoji allows you to choose separate skin tones for each hand

FaceTime
- SharePlay sessions can be initiated directly from supported apps

Siri
- Siri can provide time and date information while offline on iPhone XS, iPhone XR, iPhone 11 or newer
- Siri now includes an additional voice, expanding the diversity of options

Vaccine cards
- EU Digital COVID Certificate support in Health enables you to download and store verifiable versions of COVID-19 vaccination, lab results, and recovery records
- COVID-19 vaccination cards in Apple Wallet now support the EU Digital COVID Certificate format

This release also includes the following enhancements for your iPhone:
- Safari webpage translation adds support for Italian and Chinese (Traditional)
- Podcasts app adds episode filters for seasons, played, unplayed, saved, or downloaded episodes
- iCloud custom email domains can be managed from Settings
- News offers enhanced discovery of audio content in the Today feed and Audio tab
- Camera in keyboard can be used to add text to Notes and Reminders
- Shortcuts now supports adding, removing, or querying tags with Reminders
- Emergency SOS settings have changed to use Call with Hold for all users. Call with 5 Presses is still available as an option in Emergency SOS settings
- Close-up in Magnifier uses the ultra-wide camera on iPhone 13 Pro and iPhone 13 Pro Max to help you see small objects
- Saved passwords can now include your own notes in Settings

This release also includes bug fixes for your iPhone:
- Keyboard may insert period between typed numbers
- News widgets in Today View may not open articles when tapped
- Photos and videos may not sync to iCloud Photo Library
- Speak Screen Accessibility feature may quit unexpectedly within the Books app
- Live Listen may not turn off when switched off in Control Center

Some features may not be available for all regions or on all Apple devices. For information on the security content of Apple software updates, please visit this website: https://support.apple.com/kb/HT201222

For a complete overview of all of the features that are available in iOS 15, we have a dedicated iOS 15 roundup.

Source: Macrumors