iOS 4 was the fourth major release of Apple's mobile software and the first to carry the shortened name iOS. Announced and developed by Apple Inc., it shipped to users in mid‑2010 and marked a significant change in the platform’s user experience and developer capabilities. The update brought features that altered how apps ran, how the Home Screen could be organized, and how developers integrated services into their software. It was notable as the first update that iPod Touch owners could obtain free of charge.
Key features
At the user level iOS 4 introduced multitasking support for third‑party applications, organized apps into Home Screen folders, and allowed some devices to display a custom wallpaper behind app icons. The release also improved mail handling by offering a unified inbox and added platform services that enabled in‑app advertising and richer background services. Apple promoted a large expansion of capabilities for programmers, saying the release provided more than 1,500 new APIs and frameworks to extend app behavior and integrate system features.
Compatibility and limitations
Not all Apple mobile devices received the same feature set under iOS 4. Support ranged by model and hardware capability:
- Full feature support was available on more recent models of the era, such as the iPhone 4 and iPhone 3GS, and later iPod Touch models.
- Some older devices — notably the iPhone 3G and the 2nd‑generation iPod Touch — could install iOS 4 but were restricted: they did not offer the complete multitasking experience and lacked Home Screen wallpaper among other features.
- The original iPhone and first‑generation iPod Touch were not able to upgrade to iOS 4 at all, remaining on earlier releases of the operating system.
Updates and unification with iPad
Apple continued to refine iOS 4 after its initial launch. A notable follow‑up was iOS 4.2.1, released later in 2010, which extended support to the iPad and helped bring parity between Apple’s phone and tablet software. That update is remembered as the point at which iPhone and iPad software lines were more tightly unified on the same operating system, simplifying development and feature expectations across devices. For some older models the 4.2.1 release was the final iOS version they could run.
Historical significance and legacy
iOS 4 is often cited as a turning point in the iPhone platform because it moved the system toward the multitasking, multitiered app ecosystem that defines later mobile OS releases. By adding developer APIs, background execution modes and new user interface conventions, the update set the stage for richer third‑party apps and more complex system services. It also formalized the modern product name, helping establish "iOS" as the brand for Apple's mobile operating system family.
For additional technical details, developer notes and device lists consult official documentation and device support pages via the vendor and developer channels: iOS overview, Apple, iPod Touch, iPad, iPhone, APIs, OS unification.