You can download iOS 15.4 IPSW firmware files for all devices from this page. This firmware file can be restored with iTunes if and only if it is still being signed by the time you download. Note that our website provides firmware directly from Apple's server using the ipsw.me API.
IPSW, iPhone Software, is a file format used to install iOS, iPadOS, tvOS, HomePod, and most recently, macOS firmware for devices equipped with Apple silicon.
You can check this post to get the correct firmware identifier for your iDevices.
iOS 15.4 Release notes
- 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
- 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
- SharePlay sessions can be initiated directly from supported apps
- 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
- 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
- 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 the 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
- Keyboard may insert a 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