[2] iOS 4 introduced many features that have since become commonplace, such as folders on the home screen, significantly increasing the number of apps that can be displayed.

Support for home screen wallpapers on the iPhone was also added, although limited to newer devices due to animation performance requirements.

Around the same time, the release of iPhone 4 and its subsequent antenna problems made Apple focus on unsuccessfully attempting to patch the issues with software updates.

At the WWDC keynote address on June 7, 2010, it was renamed to iOS 4 in order to be more inclusive to the iPod Touch and iPad.

[3] iOS 4 raised the maximum number of home screen apps from 180 to 2,160 due to the addition of folders.

The feature allowed users to switch between apps instantly by clicking the home button two times.

[6][7] This feature was notably absent from iPhone 3G and the second-generation iPod Touch due to performance issues.

[11] It also gained support for MobileMe e-mail aliases and multiple Exchange accounts for business users.

The Safari mobile web browser on iOS 4 added Bing as a search option in addition to Google and Yahoo!.

[17] In November, Apple was sued for the issues, with an unsatisfied customer alleging "violating the Consumer Legal Remedies Act, unfair business practices, and false and deceptive advertising", with further allegations that Apple knew its software would cause problems on older models.

Apple never responded to the allegations, but wrote in a reply to another unsatisfied customer in August 2010 that updates were "coming soon".