To iOS 4 είναι συμβατό με το iPhone 4, iPhone 3GS, iPhone 3G, iPod touch 2G και iPod touch 3G αλλά δεν είναι όλα τα χαρακτηριστικά διαθέσιμα για όλες τις συσκευές:
"Not all features are compatible with all devices. For example, multitasking, custom wallpaper, and Bluetooth keyboard support are available only with iPhone 4, iPhone 3GS, and the third-generation iPod touch (32GB and 64GB models from late 2009)."
Πριν προχωρήσετε στην αναβάθμιση της συσκευής σας έχετε υπόψιν σας τα παρακάτω:
- Όσοι επιθυμείτε να διατηρήσετε το jailbreak/unlock της συσκευής σας καλό θα ήταν να περιμένετε μέχρι να κυκλοφορήσουν τα αντίστοιχα εργαλεία (redsn0w, pwnagetool, ultrasn0w) πρωτού κάνετε την αναβάθμιση.
- Θα χρειαστεί να αναβαθμίσετε το iTunes στην έκδοση 9.2
- Συνιστούμε πάντα να αναβαθμίζετε μέσω Restore στο iTunes για να αποφύγετε τυχόν παρενέργειες.
- Φροντίστε να κάνετε ένα τελευταίο συγχρονισμό (sync) των δεδομένων σας για να μην χάσετε επαφές/σημειώσεις/κτλπ. Μετά το Restore επιλέξτε "Set as new device" στο iTunes, ώστε να έχετε μια «καθαρή» συσκευή χωρίς «σκουπίδια» από προηγούμενα firmwares.
- Όσοι δεν νοιάζεστε για το jailbreak/unlock μπορείτε να αναβαθμίσετε άφοβα.
iOS 4 changelog:
* - Multitasking support for third-party apps*
* - Multitasking user interface to quickly move between apps
* - Support for audio apps to play in the background
* - VoIP apps can receive and maintain calls in the
* background or when device is asleep
* - Apps can monitor location and take action while running in the background
* - Alerts and messages can be pushed to apps using
* push and local notifications
* - Apps can complete tasks in the background
* - Folders to better organize and access apps
* - Home screen Wallpaper*
* - Mail improvements
* - Unified inbox to view emails from all accounts in one place
* - Fast inbox switching to quickly switch between different email accounts
* - Threaded messages to view multiple emails from the same conversation
* - Attachments can be opened with compatible third- party apps
* - Search results can now be filed or deleted
* - Option to select size of photo attachments
* - Messages in the Outbox can be edited or deleted
* - Support for iBooks and iBookstore (available from the App Store)
* - Photo and Camera improvements
* - 5x digital zoom when taking a photo**
* - Tap to focus during video recording**
* - Ability to sync Faces from iPhoto
* - Geo-tagged photos appear on a map in Photos
* - Ability to create and edit playlists on device
* - Calendar invitations can be sent and accepted wirelessly with supported CalDAV servers
* - Support for MobileMe calendar sharing
* - Suggestions and recent searches appear during a web search
* - Searchable SMS/MMS messages**
* - Spotlight search can be continued on web and Wikipedia
* - Enhanced location privacy
* - New Location Services icon in the status bar
* - Indication of which apps have requested your location in the last 24 hours
* - Location Services can be toggled on or off for individual apps
* - Automatic spellcheck
* - Support for Bluetooth keyboards*
* - iPod out to navigate music, podcasts and audiobooks through an iPod interface with compatible cars
* - Support for iTunes gifting of apps
* - Wireless notes syncing with IMAP-based mail accounts
* - Persistent WiFi connection to receive push notifications*
* - New setting for turning on/off cellular data only**
* - Option to display the character count while composing new SMS/MMS**
* - Visual Voicemail messages can be kept locally even if
* they have been deleted from the server**
* - Control to lock portrait orientation*
* - Audio playback controls for iPod and third-party audio apps*
* - New languages, dictionaries and keyboards
* - Accessibility enhancements*
* - Bluetooth improvements
* - Better data protection using the device passcode as an encryption key* (Requires full restore.)
* - Support for third-party Mobile Device Management solutions
* - Enables wireless distribution of enterprise applications
* - Exchange Server 2010 compatibility
* - Support for multiple Exchange ActiveSync accounts
* - Support for Juniper Junos Pulse and Cisco AnyConnect SSL VPN apps (available from the App Store)
* - More than 1,500 new developer APIs
