iOS 4

iOS 4 is the <a href="/facts/IOS_version_history/4CILLmV7">fourth major release</a> of the <a href="/facts/IOS/mK5cggH5">iOS</a> <a href="/facts/Mobile_operating_system/wysBVca1">mobile operating system</a> developed by <a href="/facts/Apple_Inc./oTJYta3k">Apple Inc.</a>, being the successor to <a href="/facts/IPhone_OS_3/qgqxDLxY">iPhone OS 3</a>. It was announced at the Apple Special Event on April 8, 2010, and released on June 21, 2010. iOS 4 was the first version branded as "iOS" rather than "iPhone OS", due to the release of the <a href="/facts/IPad/Ql67x0Dw">iPad</a>. It was succeeded by <a href="/facts/IOS_5/vTcoFvkC">iOS 5</a> on October 12, 2011.
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. The operating system also added a multitasking feature, letting apps dealing with <a href="/facts/Voice_over_IP/5QGBbXYg">Internet calling</a>, <a href="/facts/Global_Positioning_System/DKVLnzF3">location</a> and audio playback function in the background, whereas a similar but more restricted "Fast App Switching" technology enabled any app to be left inactive in the background while users switch to other apps. iOS 4 also added a system-wide spell checking feature, enabled <a href="/facts/Apple_Books/8nav1dFN">iBooks</a> on iPhone, unified the <a href="/facts/Mail_(Apple)/MQaA2wRe">Mail</a> inbox to combine content from different email providers, and introduced both <a href="/facts/Game_Center/b700roto">Game Center</a> for social gaming and <a href="/facts/FaceTime/EBzVmbfe">FaceTime</a> for <a href="/facts/Videotelephony/Ya9TMFQD">video calling</a>.
The iOS 4 update introduced performance and battery problems on <a href="/facts/IPhone_3G/SRS78a4T">iPhone 3G</a> devices, with Apple investigating the matter and promising then-upcoming updates. However, the company became the subject of a lawsuit from an unsatisfied customer over the issues. Around the same time, the release of <a href="/facts/IPhone_4/EWe0sE18">iPhone 4</a> and its subsequent <a href="/facts/Antennagate/EWe0sE18">antenna problems</a> made Apple focus on unsuccessfully attempting to <a href="/facts/Patch_(computing)/sIHVBPls">patch</a> the issues with software updates.
iOS 4 is the final version of iOS that features the iPod app for music and videos on iPhones and iPads. Starting with iOS 5, iPhones and iPads do not have the iPod app, but instead have the Music and Videos apps, as the <a href="/facts/IPod_Touch/PRJabx51">iPod Touch</a> does. It is also the last version of iOS that supports the iPhone 3G and <a href="/facts/IPod_Touch_(2nd_generation)/PRJabx51">second-generation iPod Touch</a>, up to version 4.2.1 (4.3 dropped support for both devices), due to hardware limitations and performance issues.

iOS 4 open-in-new

iOS 4