iOS 4

Apple previewed the beta as iPhone OS 4 on April 8, 2010; by the June 7 iPhone 4 announcement it called the system iOS 4. These are names for the same major version, not two separate systems. Apple announced the free update for June 21 through iTunes 9.2 or later.

Original typographic card; not a historical screenshot.

Type: Operating system
Family: iOS
Major version: 4
Preview: 2010-04-08
Announced availability: 2010-06-21
Initial distribution: iTunes 9.2+
Upgrade price: Free
Main changes: Folders · unified Mail · limited multitasking
Documented updates: 4.0 · 4.1 · 4.2 · 4.3
Limit: System support does not imply support for every feature.

Folders group applications, while Mail adds a unified inbox and threaded messages. Third-party multitasking has hardware limits: Apple specifies iPhone 3GS, iPhone 4 and third-generation iPod touch or later, not iPhone 3G or second-generation touch.

Updates expand this same entry. Fourth-generation iPod touch was introduced with iOS 4.1; on November 22, 2010 Apple announced iOS 4.2 available for download, bringing multitasking, folders and other features to the original iPad. iPad 2 came with iOS 4.3, which added improvements to Safari, Home Sharing and AirPlay.

Compatibility is stated by version and variant, not similarity of names. The iOS 4.3 list specifies GSM iPhone 4; the Verizon iPhone 4 announcement documents iOS 4 without naming a minor revision. The entry distinguishes factory software from official upgrades and does not equate system compatibility with support for every feature.