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iOS 4
Version of the iOS operating system
iOS 4.1 home screen on an iPhone 3GS
DeveloperApple Inc.
Source modelClosed, with open source components
Initial releaseJune 21, 2010; 15 years ago (2010-06-21)
Latest release
iPhone 3G, iPod Touch (2nd generation)

4.2.1 (November 22, 2010; 15 years ago (2010-11-22)) [±]

iPhone 4 (CDMA)

4.2.10 (July 25, 2011; 14 years ago (2011-07-25)) [±]

iPhone 3GS, iPhone 4 (GSM), iPod Touch (3rd generation), iPod Touch (4th generation), iPad (1st generation), iPad 2
4.3.5 (July 25, 2011; 14 years ago (2011-07-25)) [±]
Update methodiTunes through a computer
Package managerApp Store
Supported platformsiPhone, iPod Touch, iPad
Kernel typeHybrid (XNU)
LicenseProprietary EULA except for open-source components
Preceded byiPhone OS 3
Succeeded byiOS 5
Official websiteApple – iPhone – New features in the iOS 4 Update at the Wayback Machine (archived June 30, 2010)
Support status
Obsolete, unsupported.[citation needed] Drops support for the iPhone (1st generation) and the iPod Touch (1st generation).

iOS 4 is the fourth major release of the iOS mobile operating system developed by Apple Inc., being the successor to iPhone OS 3. 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",[1] due to the release of the iPad. It was succeeded by iOS 5 on October 12, 2011.[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. The operating system also added a multitasking feature, letting apps dealing with Internet calling, location 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 iBooks on iPhone, unified the Mail inbox to combine content from different email providers, and introduced both Game Center for social gaming and FaceTime for video calling.

The iOS 4 update introduced performance and battery problems on iPhone 3G 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 iPhone 4 and its subsequent antenna problems made Apple focus on unsuccessfully attempting to patch 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; they have, instead, separate Music and Videos apps, matching what the iPod Touch has. It is also the last version of iOS that supports the iPhone 3G and second-generation iPod Touch, up to version 4.2.1 (4.3 dropped support for both devices), due to hardware limitations and performance issues.

Apps

[edit]

History

[edit]

iOS 4 was introduced at the Apple Special Event on April 8, 2010. At the WWDC keynote address on June 7, 2010, it was named iOS 4 and not iPhone OS 4 in order to be more inclusive to the iPod Touch and iPad.[3]

iOS 4 was officially released on June 21, 2010.[3]

System features

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Folders

[edit]

iOS 4 added folders for apps, which raises the maximum number of home screen apps from 180 to 2,160. These folders would automatically be named based on the containing apps' respective App Store category.[4]

Multitasking

[edit]

iOS 4 introduced multitasking, replacing the home button shortcuts feature which had a similar albeit more limited function. It allows users to switch between apps instantly by clicking the home button two times. It was implemented in such a way that did not cause excessive battery drain. Multitasking was limited to apps dealing with Internet calling, location, and audio playback, while a similar "Fast App Switching" technology meant users could leave an app and enter another, with the original app remaining in the background until the user returns.[5][6] This feature was notably absent from iPhone 3G and the second-generation iPod Touch due to performance issues.

iOS 4 introduced a spell checking feature that underlined misspelled words in red. Tapping on the word would provide a pop-up with a recommended replacement.[7]

Camera

[edit]

The Camera app now supports 5x digital zoom.[8]

Apps

[edit]

The Mail app featured a unified inbox on iOS 4, allowing users to see messages from all of their email accounts displayed together in a single inbox.[9] It also gained support for MobileMe e-mail aliases and multiple Exchange accounts for business users.[5]

iOS 4.1 added a new app called Game Center, an online multiplayer social gaming network, which allows users to invite friends to play games and to compare their scores on a leaderboard.[10][11] It was not available on the iPhone 3G.[11]

FaceTime

[edit]

iOS 4 introduced FaceTime, a videotelephony app that uses the device's camera to allow the user to make video calls with other FaceTime users.[12] This feature was absent from the iPhone 3G, second-generation iPod Touch, iPhone 3GS, and third-generation iPod Touch due to the lack of required features, such as a front-facing camera.

Safari

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The Safari mobile web browser on iOS 4 added Bing as a search option in addition to Google and Yahoo!.[13] Beginning with iOS 4.2.1, specific words or phrases on a page could be searched.[14]

Features added on the iPhone inherited from the iPad

[edit]

On the iPhone, the ability to choose wallpapers and see them on the home screen was also added, and the iPad had its ones replaced to be consistent, though the feature was notably absent from iPhone 3G and the second-generation iPod Touch due to poor performance of icon animations.[15]

The iPhone's dock was updated to be skeuomorphic, as with the Dock on the iPad and Mac OS X, and no longer has a grey line underneath it; the icons were redesigned to match.

iOS 4 introduced iPhone and iPod Touch support in iBooks, which was already included on the iPad. Though not a default app, it was available through the App Store.[16]

Problems

[edit]

Performance and battery issues

[edit]

iPhone 3G users reported performance and battery issues after upgrading to iOS 4. Apple started an investigation of the matter in July 2010.[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".[18][19]

Alarm clock

[edit]

In all versions of iOS 4, the alarm clock in the clock app had a problem in DST when it would go off an hour too early or too late.[20]

Antenna problems

[edit]

Upon its release, some iPhone 4 users reported having technical problems with the phone's antennas.[21] Apple attempted to fix the issue in software with iOS 4.0.1,[22] but failed to do so.[23]

Supported devices

[edit]

iOS 4 drops support for the first-generation iPhone and first-generation iPod Touch. The first-generation iPod Touch did not receive support due to hardware limitations. This marks the first time Apple has dropped support for an iPhone while retaining support for another model featuring the same or a less powerful system on a chip. The iPhone 3GS and iPod Touch (3rd generation) has partial support, and the iPhone 3G and iPod Touch (2nd generation) have limited support.[a]

Version history

[edit]
Version Build Codename Release date Notes Update type
4.0 8A293 Apex June 21, 2010[3] Initial release for iPhone 4 GSM
  • Allows use of multiple Mail inboxes
  • Adds support for folders for app organization
  • Allows creation of music playlists
  • Introduces the iBooks app
  • Adds tap-to-focus in the Camera app
  • Allows uses of Bluetooth keyboards
  • Allows users to gift apps to other Apple IDs in the App Store, as long as those apps contained no fraudulent information
  • Adds spellcheck
  • iPhone 3GS and iPhone 4 only:
    • Adds support for multitasking
    • Adds support for setting a home screen wallpaper
  • iPhone 4 only:
    • LED flash for camera
    • 5x digital camera zoom
    • FaceTime
 Initial Release
4.0.1 8A306 July 15, 2010 Only for iPhone
  • Changes the algorithm that displays cellular signal strength after Antennagate[24]
  • Fixes a bug with Microsoft Exchange accounts
 Bug Fixes
4.0.2 8A400 August 11, 2010
  • Fixes a bug that allowed a maliciously crafted PDF to lead to arbitrary code execution[25]
  • Fixes a bug that allows code running as user to gain system privileges

Due to all these patches, JailbreakMe 2.0 stops working.

Bug Fixes
4.1 8B117
8B118[b] 		Baker September 8, 2010 Initial release on iPod Touch (4th generation)
  • Adds HDR photo capture support to the iPhone 4
  • Allows upload of high definition videos captured on the iPhone 4 to YouTube and MobileMe
  • Fixes a bug that allowed a maliciously crafted .tiff image to lead to arbitrary code execution[26]
  • Fixes a bug that allowed an attacker in a privileged network position to redirect FaceTime calls
  • Fixes multiple bugs that caused visiting a maliciously crafted website to lead to arbitrary code execution
  • Exclusive to iPhone 3GS, iPhone 4, and iPod touch (2nd and 3rd generation):
    • Game Center, a service that allows syncing of game save data, achievements, and more. Game Center had previously been part of developer versions of iOS 4.[27]
 Feature Update
4.2 8C134 Unknown November 1, 2010[28]
  • Adds AirPlay, allowing devices to stream audio or video to the Apple TV (1st generation)
  • Adds AirPrint, allowing devices to print wirelessly to some HP ePrint printers
  • Allows users to create a free MobileMe account to access Find My iPhone, which allows location tracking and remote locking or wiping of a device
  • Adds support for the iPad (1st generation)
  • Birthdays calendar does not display birthdays starting more than 77 years ago.
  • Fixes glitch that can let a user get into the Phone app while the phone is locked via "Emergency Call" by dialing a random number and quickly pressing the lock button after dialing that call.
  • Improved iPhone 3G and iPod Touch (2nd generation) performance.
  • Import .ics calendar files directly for events.
  • Improved battery performance.
  • Birthdays icon has been changed in the Calendar app.
  • Text search on web pages. (iPhone 3GS and iPod touch 3 and 4 only)
  • 2 new fonts for Notes in Settings (Helvetica and Chalkboard).

Added support for Chinese URL over Safari.

  • Added an indicator in the App Store which shows if an app supports Game Center.
  • Support for CoreMIDI.
  • YouTube voting.
  • Minor improvements in UI graphics.
  • New parental controls for deleting apps, changing mail accounts and location services.[29]
  • The font size of text in Calendar can now be changed in the Accessibility settings.

Fixes Voice over IP (VoIP) issues. Find My iPhone location feature is free (iPhone 4, iPod Touch (4th generation), and iPad) running on iOS 4.2.1.

  • More than 30 new keyboards and dictionaries, including Arabic, Greek, and Hebrew.
  • New animation for Multitasking.

New bookmarks design (iPhone and iPod Touch only).

  • New Voice Memos icon.
  • Ability to initiate FaceTime calls from Voice Control. (iPhone 4 only)

FaceTime shortcut from Messages app (iPhone 4 only).

  • New text tone alerts (New and Original tone lists) (iPhone 4 only).

Ringer and alerts on/off switch (Settings > Sounds) for volume buttons (iPhone only).

  • Assign different text tone alerts to each contact.
 Feature Update
4.2.1[c] 8C148
8C148a[d] 		Jasper November 22, 2010[31] Last version of iOS to run on iPhone 3G and iPod Touch (2nd generation) due to hardware and performance issues.
  • Replaces iOS 4.2 as iOS 4.2 prevented Wi-Fi from working on the iPad (1st generation), iOS 4.2 was later pulled from public view
 Bug Fixes
All devices except for iPhone 4 (CDMA), iPhone 3G, and iPod Touch (2nd generation)
4.3 8F190
8F191[e] 		Durango March 4, 2011 Initial release on iPad 2
  • Adds personal hotspot to the iPhone 4 (GSM)
  • Introduces iTunes home sharing
  • Improves AirPlay[32][33]
  • Fixes multiple vulnerabilities in FreeType
  • Fixes multiple bugs that caused viewing maliciously crafted .tiff images to lead to arbitrary code execution
  • Fixes many, many bugs in WebKit that caused viewing a maliciously crafted website to lead to arbitrary code execution
  • Fixes a bug that allowed an attacker connected to the same network as an iPhone to be able to trigger a remote reset
 Initial Release, Feature Update
4.3.1 8G4 March 25, 2011
  • Fixes iPod touch screen glitches
  • Fixes bugs that prevented activation and connection of iPhones[34]
  • Fixes image flicker when using Apple Digital AV Adapter
  • Resolves an issue authenticating with some enterprise web services[35]
 Bug Fixes
4.3.2 8H7
8H8[f] 		April 14, 2011
  • Fixes a bug that caused FaceTime calls to freeze
  • Fixes connectivity issues on cellular-equipped iPads
  • Updates SSL certificates after fraudulent certificates were issued by a Comodo affiliate registration authority
  • Fixes multiple bugs that caused viewing of a maliciously crafted website to lead to arbitrary code execution[36]
 Bug Fixes
4.3.3 8J2 May 4, 2011
  • Fixes a bug that caused location to be reported incorrectly[37]
 Bug Fixes
4.3.4 8K2 July 15, 2011
  • Fixes bugs that caused viewing a maliciously crafted PDF to cause arbitrary code execution
  • Fixes a bug that caused code running as user to gain system privileges[38]

It also patches the latest version of JailbreakMe (JailbreakMe 3.0).

Bug Fixes
4.3.5 8L1 July 25, 2011
  • Fixes a bug that allowed an attacker in a privileged network position to capture and/or modify data in SSL/TLS-protected network sessions[39]
 Bug Fixes
iPhone 4 (CDMA) only
4.2.5 8E128 Unknown January 11, 2011 Preview release on iPhone 4 (CDMA). Only available to the press, never shipped on release devices Preview Release
4.2.6 8E200 Phoenix January 31, 2011 Initial release on iPhone 4 (CDMA), as 4.2.5 was preloaded at the factory, 4.2.6 was the first public version.
  • Bug fixes for personal hotspots
 Initial Release
4.2.7 8E303 April 14, 2011
  • Fixes a bug that caused FaceTime calls to freeze
  • Updates SSL certificates after fraudulent certificates were issued by a Comodo affiliate registration authority
  • Fixes multiple bugs that caused viewing of a maliciously crafted website to lead to arbitrary code execution[36]
 Bug Fixes
4.2.8 8E401 May 4, 2011
  • Fixes a bug that caused location to be reported incorrectly[37]
 Bug Fixes
4.2.9 8E501 July 15, 2011
  • Fixes bugs that caused viewing a maliciously crafted PDF to cause arbitrary code execution
  • Fixes a bug that caused code running as user to gain system privileges[38]

It also patches the latest version of JailbreakMe (JailbreakMe 3.0).

Bug Fixes
4.2.10 8E600 July 25, 2011
  • Fixes a bug that allowed an attacker in a privileged network position to capture and/or modify data in SSL/TLS-protected network sessions[39]
 Bug Fixes
  1. ^ Multitasking, home screen wallpapers and Bluetooth keyboard support are not available on both the iPhone 3G and iPod Touch (2nd generation), while Game Center, Apple's gaming network, was available on the iPod Touch (2nd generation) but not on the iPhone 3G. FaceTime is not supported on iPhone 3G and 3GS, and the iPod Touch 2nd and 3rd generations.
  2. ^ iPod Touch (4th generation) only
  3. ^ No public release of iOS 4.2 is available, due to an issue that impacted Wi-Fi functionality on the iPad.[30]
  4. ^ iPhone 3GS only
  5. ^ iPad 2 only
  6. ^ iPad 2 (CDMA) only

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

IOS 4

View on Grokipedia
from Grokipedia
iOS 4 is the fourth major release of the iOS mobile operating system developed by for its , , and devices, initially previewed as iPhone OS 4 on April 8, 2010, before being renamed iOS 4 on June 7, 2010, to encompass its broader ecosystem beyond just the . Released to the public on June 21, 2010—three days before the debut—it marked a pivotal update by introducing over 100 new features, including true multitasking for third-party apps, customizable home screen folders, and enhanced enterprise support, while requiring devices like the or later for full functionality. The update emphasized productivity and user experience enhancements, such as a unified inbox for multiple accounts with threaded conversations, customization for the , and improved with faster rendering and on-page search. It also debuted Apple's iAd platform for in-app advertising without leaving apps, alongside the iBooks app and store for users, and previewed for social gaming features like leaderboards and multiplayer matchmaking, which launched later in 2010. Multitasking was limited to seven background services—such as VoIP, audio playback, and location updates—to preserve battery life on older hardware, while newer devices gained access to app switching via a double-tap of the home button. iOS 4 supported the iPhone 3G and later, iPod Touch 2nd generation and later (with limitations on multitasking for pre-3rd gen models), and the original iPad, though some features like iBooks were iPad-exclusive at launch. The version family extended through incremental updates, including iOS 4.1 in September 2010 (adding Game Center, HDR photos, and faster animations), iOS 4.2 in November 2010 (unifying iPad and iPhone features with AirPlay and AirPrint), and iOS 4.3 in March 2011 (introducing personal hotspot and AirPlay mirroring), before being succeeded by iOS 5 in 2011. These releases collectively over 1,500 new APIs for developers, fostering richer app ecosystems while prioritizing security and performance.

Development and announcement

Development process

Development of iOS 4 commenced in late 2009, immediately following the release of iPhone OS 3.1 in 2009, with a primary focus on porting select features to the platform and implementing native multitasking support. This timeline aligned with early prototyping efforts for the accompanying hardware, where initial iOS 4 builds were integrated to test core system behaviors. The engineering objectives centered on enhancing third-party app functionality through limited background processing, all while preserving device battery efficiency and smooth operation on resource-constrained models like the . These priorities addressed longstanding user demands for productivity tools without sacrificing the responsive that defined prior OS versions. Multitasking, in particular, required innovative restrictions to mitigate performance impacts. Cross-team collaboration was essential, uniting and software engineers under Scott Forstall's leadership to consolidate and adapt the underlying OS framework for shared compatibility. This unification effort streamlined code sharing, reducing redundancy and enabling faster iteration on device-agnostic components. Throughout the process, internal beta distributions were conducted to evaluate system stability across compatible hardware, with rigorous emphasis on memory allocation and garbage collection optimizations to prevent crashes or slowdowns during background operations.

Public announcement

iOS 4 was publicly announced on April 8, 2010, at Apple's special media event held at its Cupertino headquarters, positioned as the successor to iPhone OS 3. The event, attended by journalists and developers, featured a keynote by Apple CEO , who unveiled over 100 new user features and more than 1,500 new APIs for the upcoming operating system update. Initially presented under the name iPhone OS 4, it was later rebranded as iOS 4 during Apple's on June 7, 2010, to emphasize its expanded support across Apple's ecosystem, including the , , and . During the presentation, Jobs emphasized two flagship additions: true multitasking for third-party applications, enabling background execution for tasks like audio playback and VoIP calls while optimizing battery life, and folders for organizing icons by dragging one app onto another, potentially accommodating over 2,000 apps. He demonstrated these features live, highlighting how they addressed longstanding user requests for improved productivity and interface efficiency on mobile devices. The also provided previews of several refinements, including a unified inbox that aggregates email from multiple accounts with threaded conversations and direct attachment support, customizable wallpapers for the home and lock screens selectable from built-in options or personal photos, and keyboard compatibility for enhanced input on supported devices. These teasers underscored Apple's focus on making the platform more versatile and iPad-aligned, with a beta version made available to developers immediately following the event for testing ahead of the summer release.

Release and versions

Initial release

iOS 4.0 was initially released to the public on June 21, 2010, as a free software update distributed via for compatible devices including the , , third-generation , and second-generation . The update required iTunes 9.2 or later and had a download size of approximately 300 MB, depending on the device model. Adoption of the update was rapid in the weeks following launch, with analytics showing that more than 50% of active users had installed iOS 4 by late 2010. Support for the was not included in the initial iOS 4.0 release, as the device had launched earlier in April 2010 with iPhone OS 3.2; users gained access to iOS 4 features starting with the iOS 4.2 update in November 2010.

Major updates

iOS 4.1, released on September 8, 2010, addressed significant battery drain issues reported in the initial iOS 4.0 rollout, alongside performance improvements for older devices like the . It introduced , Apple's social gaming network that allowed users to compete with friends, track achievements, and discover leaderboards across compatible apps. Additionally, the update enabled direct Wi-Fi uploading of high-definition (HD) videos recorded on the to services like and , enhancing content sharing without quality loss. iOS 4.2, released on November 22, 2010, extended core iOS 4 features to the for the first time, with the iPad version appearing as 4.2.1 in the due to minor build differences. It introduced for wireless streaming of audio, video, and photos to , and for direct printing to compatible printers without needing additional software. The update also refined multitasking on the , providing faster app switching and background app refresh tailored to the device's larger screen and hardware. iOS 4.3, released on March 9, 2011, brought further refinements including Personal Hotspot, allowing users to share their cellular data connection via , , or USB with up to five devices. It added a Reading List for saving web pages for offline viewing and improved overall system animations for smoother transitions and reduced latency. This version marked the end of major feature updates for the and second-generation , as subsequent releases dropped support for those devices, though earlier versions like iOS 4.2.1 continued to receive security patches where applicable. Security updates for iOS 4 devices continued beyond the major releases for supported hardware, with the final update for older devices like the and second-generation being iOS 4.2.1, released on November 22, 2010.

Features

User interface enhancements

iOS 4 introduced several enhancements to the , improving , , and input methods across compatible devices. These changes focused on making the operating system more intuitive and visually appealing, allowing users greater control over their device's appearance and interaction flow. Key updates included options for customizing the visual backdrop of screens and refining how users access and manage content within built-in applications. One prominent addition was the ability to set customizable wallpapers for both the and . Users could select from pre-installed s provided by Apple or import personal photos synced from their computer via . To apply a wallpaper, users navigated to Settings > Wallpaper, chose an or , adjusted its position and scale, and assigned it to one or both screens. This feature enhanced the device's aesthetic personalization across all compatible devices. The Mail application received a unified inbox, which aggregated messages from multiple email accounts into a single view for streamlined access. Tapping "All Inboxes" on the Mailboxes screen displayed incoming emails from accounts like , Exchange, or other popular providers in one consolidated list, reducing the need to switch between accounts manually. This update improved overall email management efficiency. Support for external Bluetooth keyboards was added to facilitate faster text input, particularly for productivity tasks. Compatible devices, including the , could be paired through Settings > General > , enabling wireless typing across apps like and Notes. This enhancement was especially useful for users composing longer messages or documents on the go. iOS 4 also incorporated an emoji keyboard for adding expressive icons to messages and other text fields. Accessible via international keyboard settings under General > Keyboard > International Keyboards > Add New Keyboard > , it provided a dedicated layout for symbols, particularly prominent on Japanese iPhone models but available globally. Users could switch to it during typing for enhanced communication in apps like Messages. Additionally, folders for app organization were introduced, enabling users to drag one onto another to create customizable groups, which briefly ties into broader navigation improvements without altering core UI aesthetics.

Multitasking and background processes

iOS 4 marked the first introduction of multitasking capabilities to the iPhone operating system, allowing users to switch between applications without fully closing them and enabling select background processes to continue running. This feature addressed long-standing user demands for improved productivity on mobile devices, while prioritizing battery life and performance through a suspend-and-resume model rather than true concurrent execution for most apps. Users access the multitasking interface by double-clicking the Home button, which reveals a horizontal displaying and snapshots of recently used applications at the bottom of the screen. Swiping left or right navigates through the tray, and tapping an brings the corresponding app to the foreground, resuming it from its previous state. The system supports maintaining multiple apps in this suspended state, though the practical limit depends on available RAM; the system automatically purges older ones to free when necessary. Beyond simple switching, iOS 4 permitted specific types of background execution for third-party apps, including audio playback (such as music or streaming), (VoIP) services for calls, location updates for navigation or tracking, and local notifications to alert users without foreground activity. Developers enabled these by declaring the appropriate modes in the app's Info.plist file, such as "audio" for background sound or "voip" for telephony. Additionally, apps could request finite background time (up to about 10 minutes) to complete tasks like downloading content after transitioning to the background. These capabilities were designed to support essential functions without excessive resource use. A core mechanism enabling efficient switching was fast app switching, where backgrounded apps entered a suspended state: the system captured a snapshot of the app's interface for visual representation in the switcher and preserved its memory state on disk without ongoing CPU execution. Upon reactivation, the app resumed nearly instantaneously from this saved state, avoiding the need for a full reload and minimizing launch times to under a second in most cases. This approach ensured a responsive while conserving power, as suspended apps consumed no battery. Full multitasking was available only on devices with sufficient hardware, specifically the iPhone 3GS and later models, iPod touch 3rd generation and later, and the original iPad; the iPhone 3G and iPod touch 2nd generation supported iOS 4 but lacked true multitasking, limiting them to basic background audio playback while terminating other apps upon switching. Developers could detect support via the UIApplication class's isMultitaskingSupported property to adapt behavior accordingly. To optimize battery life, iOS 4 automatically suspended inactive background apps after a short period, halting all execution except for approved modes like audio or location; apps were encouraged to release unnecessary resources during suspension to avoid system-forced termination under low conditions. This design balanced functionality with the constraints of mobile hardware, preventing the rapid battery drain seen in full desktop-style multitasking.

App organization and management

iOS 4 introduced folders as a primary tool for organizing apps on the , allowing users to create custom groupings by dragging one app onto another, which automatically generates a new folder. The system suggests a default name based on the category of the apps involved, such as "Games" or "Utilities," though users could rename folders manually for personalized . Each folder supported up to 12 apps in a 4x3 grid layout, enabling efficient consolidation of related applications without expanding the overall footprint on the . Folders themselves could be placed anywhere on the pages or even in the for faster access, effectively extending the organizational capacity beyond the standard 16 per page (excluding the ). The in iOS 4 accommodated up to 11 pages of icons, providing space for hundreds of apps while maintaining navigability through horizontal swiping. To address potential clutter from this expanded layout, iOS 4 enhanced Universal Search—accessed by swiping left from the first or using Spotlight—which allowed users to quickly locate and launch apps, contacts, emails, music, and other content without browsing pages manually. This search functionality integrated app results prominently, reducing the time spent on static organization and complementing dynamic features like app switching in multitasking. App management extended to installation and maintenance through the App Store, where over-the-air (OTA) updates enabled direct downloads and installations on the device via Wi-Fi, minimizing reliance on iTunes syncing for routine upkeep. Users accessed the Updates tab in the App Store app to check for available versions, review release notes, and apply changes wirelessly, streamlining the process for the growing library of over 185,000 apps available at the time. This OTA approach supported both free and paid apps without distinction in the update workflow, ensuring consistent management across the ecosystem. For ongoing organization, iOS 4 improved app badges, which displayed numeric indicators on icons to signify unread messages, updates, or other pending actions, helping users prioritize without opening each app. These badges integrated with the push notification framework, providing visual cues that enhanced utility alongside folders and search, while the App Store's unified search bar allowed seamless discovery of free and paid apps in a single query across categories.

Built-in application updates

iOS 4 brought several updates to the Safari web browser, including search suggestions that appear as users type in the address bar to facilitate quicker navigation. Users could also select Bing as an alternative search engine through the settings menu, expanding options beyond the default Google integration. The browser supported up to eight open tabs on iPhone and iPod Touch devices, with a built-in pop-up blocker to prevent intrusive advertisements from interrupting browsing. Additionally, Safari displayed full Web addresses and page titles while typing URLs, aiding in accurate entry and reducing errors. The Mail app received significant improvements in iOS 4, introducing a unified inbox that combined messages from multiple accounts into a single view for easier management. Threaded conversations grouped related emails together, allowing users to follow discussions more efficiently, with an option to toggle this feature in settings. Search functionality was enhanced to allow querying within emails directly from the app, and users could delete messages found in search results without opening them. Overall loading times were faster due to optimized inbox switching between accounts and better attachment handling, which now opened in compatible third-party apps. Updates to the Camera app in iOS 4, particularly with the hardware, included 5x digital zoom for both photos and videos, though image quality degraded at higher zoom levels. A grid overlay was added to assist with composition using the , helping users align subjects more precisely. Support for the enabled video calling via , with tap-to-focus available during video recording for sharper results. The Photos app in iOS 4 gained organizational enhancements, such as viewing images by faces or places using data synced from or libraries via . Basic editing tools, including and rotate options, were introduced in update 4.1, allowing users to adjust images directly in the app without external software. Notes and received minor interface adjustments in iOS 4 to better support iPad screens, ensuring consistent usability across devices while maintaining core functionality. Notes added wireless syncing via IMAP email accounts, enabling seamless access to content on multiple devices. iOS 4.1 introduced the Game Center app, enabling social gaming with features such as friend lists, leaderboards, achievements, and multiplayer matchmaking for compatible games. iOS 4 introduced the iAd network, Apple's in-app advertising platform that delivered rich, interactive ads within apps, supporting video, animations, and location awareness while keeping users engaged without app switches.

iPad-specific integrations

iOS 4 introduced several features originally developed for the 's iPhone OS 3.2, porting them to and devices while enhancing capabilities in subsequent updates. The iBooks app, launched with the original on April 3, 2010, under iPhone OS 3.2, enabled e-reading with support for and PDF formats, allowing users to organize content in a virtual bookshelf interface for easy browsing and management. This app's design leveraged the 's larger screen for immersive reading, including adjustable text sizes, annotations, and seamless syncing across devices via . In iOS 4.2, released for as version 4.2.1 on November 22, 2010, multitasking was adapted for the iPad's 9.7-inch display, providing a horizontal app switcher that displayed live previews of recent apps along the bottom of the screen, offering a preview-like view of multiple tasks without full side-by-side execution. This implementation took advantage of the expanded screen real estate to improve app switching efficiency compared to the iPhone's vertical list, while maintaining background support for audio, VoIP, and location services. Optimizations for the iPad's larger form factor included an expanded on-screen keyboard in landscape orientation, which provided a full layout for more comfortable typing, and the introduction of a split keyboard mode in iOS 4.2 to facilitate thumb-based input by dividing the keys into two halves. Additionally, support in iOS 4.2 enabled wireless mirroring of the iPad's screen to an or compatible external display, allowing video streaming and full-screen duplication for presentations or media viewing. Several iPad features from iOS 4.2 were later inherited by iPhone devices, including wireless printing via , which permitted direct output to compatible printers without a computer, and the free availability of Find My iPhone for remote location and device management. The iOS 4.2.1 update also integrated on iPad with improved multiplayer matchmaking and achievements, enhancing social gaming tailored to the device's capabilities.

Supported devices

iPhone and iPod Touch compatibility

iOS 4 was compatible with the iPhone 3G, iPhone 3GS, iPhone 4, second-generation iPod Touch, third-generation iPod Touch, and fourth-generation iPod Touch, though support varied by model with certain feature limitations on older hardware. The iPhone 3G received partial support for iOS 4, lacking full multitasking, data protection, Bluetooth keyboard support, and customizable home screen wallpapers, though it included features like folders and unified email inbox. This model was upgradable up to iOS 4.2.1. In contrast, the iPhone 3GS offered full feature support for iOS 4, including multitasking and all other enhancements, and remained compatible with updates up to iOS 6.1.6. The iPhone 4 provided complete access to iOS 4 features, including FaceTime video calling, which required its front-facing camera and specific hardware. This device supported updates up to iOS 7.1.2. For iPod Touch models, the second generation had basic iOS 4 support without multitasking or other advanced capabilities, limited to updates up to iOS 4.2.1. The third-generation iPod Touch (16 GB, 32 GB, and 64 GB variants from late 2009) received full support, while the 8 GB model had partial compatibility similar to the second generation; it was upgradable to iOS 4.2.1. The fourth-generation iPod Touch offered full iOS 4 support, including camera-related features enabled by its front and rear cameras for applications like FaceTime starting in iOS 4.1.

iPad compatibility

The first-generation iPad, released in 2010, initially shipped with iOS 3.2 and was later upgraded to versions ranging from iOS 4.2.1 to iOS 5.1.1, marking the full integration of features tailored for the device. This upgrade path began with in November 2010, which introduced over 100 new capabilities specifically for the iPad, including support for third-party multitasking. Full multitasking, allowing users to switch between apps while preserving battery life, was a key addition in , enabling background tasks such as audio playback, VoIP calls, location services, and notifications—features previously limited on the iPad compared to iPhone models. The first-generation iPad's hardware, particularly its 256 MB of RAM, imposed limitations on 4 performance, restricting the depth of multitasking and app switching compared to later devices. In contrast, the second-generation iPad, launched in March 2011, did not receive 4 support until 4.3, which shipped pre-installed on the device and extended compatibility to include enhanced features like video and photo streaming optimized for the iPad's larger 9.7-inch display. This version built on iOS 4.2 by improving wireless streaming to , taking advantage of the iPad's screen size for better media presentation without the RAM constraints of the original model. Support for the first-generation iPad ended with iOS 5.1.1, released on March 7, 2012, which served as the final security update for the device and addressed minor bugs while maintaining compatibility with its aging hardware.

Apple TV support

The second-generation Apple TV, released in September 2010, ran a stripped-down variant of iOS versions 4.1 through 4.3, optimized exclusively for media streaming and playback without the broader capabilities of mobile iOS implementations. This customized operating system powered the device's core functions, such as streaming video and audio from , , , and other services directly to a connected television via . A key integration feature was support for , introduced in iOS 4.2 for the , which enabled wireless mirroring and sharing of photos, videos, and audio from iOS 4-equipped devices like the , , and to the without physical connections. This functionality extended to full-screen video playback and multi-room audio streaming, enhancing the device's role as a hub for home entertainment sourced from iOS ecosystems. The interface drew from the iOS home screen design but was heavily simplified, featuring a grid of icons for media categories like Movies, TV Shows, and Computers, with no support for the , third-party applications, or general tasks. Navigation relied on an or iOS device controls, emphasizing seamless access to rented or streamed content rather than interactive apps. Updates to the Apple TV's software aligned with the iOS 4.x series, progressing from version 4.1 (launched with the device) to 4.3 in mid-2011, which added features like direct purchases of TV episodes and support. Beyond iOS 4.3, the device received further updates up to Apple TV Software 6.2.1 in September 2014, but its foundational architecture remained tied to the iOS 4-era limitations; Apple later shifted to the operating system starting with the fourth-generation in 2015.

Issues and criticisms

Software bugs

iOS 4's launch was marred by several software glitches that impacted core functionalities, particularly in communication and scheduling features. One prominent issue involved the , which failed to reliably turn off the when the iPhone was brought to the user's ear during calls. This led to accidental interactions, such as muting the call, activating , or ending the call prematurely, resulting in dropped calls for many users. The problem was attributed to software rather than hardware, as device replacements did not resolve it, and it affected a significant portion of calls for some early adopters. Apple addressed this in iOS 4.1 by improving sensor sensitivity to prevent inadvertent touches. The built-in Clock app also suffered from a bug related to alarm scheduling, where repeating alarms failed to trigger on the morning of changes. This affected users across regions observing the time shift, as the app misinterpreted the adjusted time, causing alarms set for weekdays or specific repeats to be skipped entirely. Apple confirmed the issue stemmed from how iOS 4 handled transitions and recommended setting non-repeating alarms as a temporary . The bug was resolved in iOS 4.2 with updated time-handling logic. Synchronization with Microsoft Exchange calendars presented another challenge, where events would fail to update properly during sessions due to sync timeouts, particularly in the initial iOS 4.0 release. Users reported issues with calendars not syncing after the update, impacting corporate users reliant on the protocol. Apple issued a configuration profile to increase sync wait times, with further improvements in later updates. FaceTime, introduced as a flagship feature in iOS 4, experienced frequent connection drops on networks, particularly those with strict NAT or firewall settings. Calls would initiate but abruptly terminate or freeze, frustrating early users attempting video communication. The problem was linked to iOS 4's initial handling of network traversal for connections, which struggled with certain router configurations. Apple mitigated this through server-side improvements and iOS 4.1 refinements to enhance connection stability. Additionally, some third-party apps implemented jailbreak detection mechanisms that produced false positives on non-jailbroken devices.

Performance and battery concerns

Upon the release of iOS 4, the introduction of multitasking led to noticeable battery drain on the , primarily attributed to background processes consuming additional power even when apps were suspended. User reports highlighted that enabling multiple background apps could reduce battery life by 10-13% during moderate use compared to iOS 3, with some experiencing up to 20% faster depletion in scenarios involving frequent app switching. On the , iOS 4 introduced slower app launch times and overall UI lag, exacerbated by the device's older hardware with limited RAM and processing power. Widespread user complaints described the interface as "functionally hopeless" for basic tasks, with many experiencing persistent sluggishness shortly after upgrading. iOS 4.0 suffered from memory leaks that contributed to frequent app crashes, particularly under multitasking loads, as unreleased memory accumulated and strained the limited resources of supported devices. These issues were partially addressed in iOS 4.1 through improved app suspension mechanisms, which better managed memory allocation and reduced crash rates by optimizing background resource handling. Devices running iOS 4 also reported overheating during prolonged multitasking sessions or video calls via the new feature, as the processor worked harder to handle concurrent tasks without adequate thermal throttling on older hardware. This was linked to increased CPU utilization from background audio and . Subsequent updates like 4.1 provided partial fixes for these performance concerns, enhancing speed and stability on affected models, though older devices such as the continued to exhibit permanent slowdowns relative to their pre-iOS 4 performance due to inherent hardware limitations. One of the most prominent hardware-related issues with iOS 4 on the iPhone 4 was antenna attenuation, commonly referred to as "Antennagate." When users gripped the device on the lower left side, their hand would bridge the external antenna bands, causing a significant drop in signal strength and a reduction in displayed signal bars from five to as low as one or zero. This phenomenon led to increased dropped calls and slower data speeds, sparking widespread criticism shortly after the iPhone 4's launch in June 2010. Apple acknowledged the issue in an open letter, attributing it partly to an inaccurate signal formula rather than a fundamental antenna design flaw, and offered free bumper cases as a temporary hardware workaround to prevent skin contact with the antenna gap. The problem's software component involved the iOS 4 signal bar overestimating reception strength, which was addressed in iOS 4.1 through a revised formula and update that more accurately reflected actual signal levels without altering the underlying hardware behavior. This update, released in September 2010, reduced the visual discrepancy but did not eliminate the physical effect entirely, as confirmed by independent tests showing persistent signal loss under specific grip conditions. Another hardware interaction issue arose with the iPhone 4's , which conflicted with certain protective cases, leading to unintended touch inputs during phone calls. The sensor, located near the top front speaker, was designed to disable the when the device was held to the ear, but thick or opaque cases often blocked or reflected light, preventing proper detection and causing the screen to remain active. This resulted in accidental muting, ending calls, or dialing unintended numbers via cheek contact, frustrating users and highlighting compatibility problems between the sensor hardware and third-party accessories. Apple resolved these proximity sensor inconsistencies in iOS 4.1 with performance improvements that enhanced reliability, particularly in low-light conditions or with case interference, reducing false activations and improving overall call handling. Some overlap existed with general software bugs, but these were primarily triggered by hardware-sensor interactions rather than pure code errors. Users of the also reported camera app crashes when rapidly switching between the rear and front-facing lenses in early iOS 4 versions. This instability manifested as the app freezing or force-closing during quick toggles, often after prolonged use or in combination with other multitasking activities, disrupting photo and video sessions. The issue stemmed from hardware-software synchronization problems in accessing the dual cameras, and while not universally experienced, it affected a notable subset of devices until subsequent updates stabilized the camera subsystem. On the fourth-generation iPod Touch running , connectivity exhibited instability, including frequent disconnections, failure to detect networks, and intermittent signal drops, particularly in areas with weaker coverage. These problems were linked to glitches in the device's hardware integration, making reliable challenging for tasks like app downloads or streaming. Apple addressed this in through targeted bug fixes that improved network stability and connection retention, restoring consistent performance without requiring hardware changes. For the first-generation iPad, iOS 4's introduction of multitasking exacerbated overheating tendencies inherent to the A4 processor and device design, though the OS itself was not the direct cause. Running multiple background apps increased CPU load on the aging hardware, leading to elevated temperatures during extended sessions, such as web browsing or media playback with suspended tasks. Users noted the device becoming uncomfortably warm, sometimes triggering throttling to prevent damage, but no specific iOS 4 patch fully mitigated this hardware limitation.

Reception and legacy

Critical and user reception

iOS 4 received widespread praise from critics for introducing long-awaited features like multitasking and app folders, which significantly enhanced user productivity on supported devices. Reviewers highlighted multitasking as a major advancement, allowing third-party apps to run in the background for tasks such as audio playback and location services, with noting it as "the biggest and most obvious update" that addressed a key limitation of prior versions. Similarly, commended the unified inbox and folders for streamlining organization, describing iOS 4 as delivering "crucial features" that iOS had lacked for years. echoed this sentiment in its iPhone 4 coverage, calling iOS 4 a "mostly terrific software upgrade" that made the platform feel more modern without major drawbacks on newer hardware. Adoption was rapid, with 50% of iPhones updated to iOS 4 within a month of release and over 80% of devices sold in the previous four years running iOS 4 or later by October 2011. However, criticisms focused on software bugs and degraded performance on older devices like the , where multitasking exacerbated slowdowns and app crashes. reported user complaints of sluggishness post-upgrade, with Apple acknowledging investigations into these hardware-software mismatches. Cult of Mac documented similar issues, noting longer app launch times and glitches that made the experience frustrating for 3G owners. These problems led to mixed user feedback, with many advising against updating legacy devices. The release of iOS 4 alongside the drove strong sales, with Apple reporting over 1.7 million units sold in the first three days, attributing much of the enthusiasm to the software's enhancements. App developers particularly welcomed the expanded APIs for background processing, which Macworld described as topping their wish lists and enabling richer applications. By the end of , the had grown to approximately 300,000 apps, reflecting the ecosystem's momentum fueled by these tools. Reception for iPad users was more mixed due to delayed full implementation of iOS 4 features; the original shipped with iPhone OS 3.2, and complete multitasking arrived only with iOS 4.2 in November 2010, leading to initial frustrations over incomplete support. Engadget's review of iOS 4.2 praised the eventual additions like folders and but noted the wait diminished early excitement.

Long-term impact

iOS 4's introduction of multitasking fundamentally shaped the evolution of Apple's mobile operating system, establishing a framework of background app execution and fast app switching that became a permanent fixture in all subsequent iOS versions, from onward. This capability, which allowed third-party apps to run limited background tasks without fully suspending them, laid essential groundwork for advanced features in , such as the for real-time alerts and for voice-activated interactions, by enabling efficient resource management and persistent processes across the system. By extending the iOS platform to the first-generation —previously limited to iPhone OS 3.x—iOS 4 unified Apple's mobile ecosystem, creating a consistent software foundation across iPhone, , and devices that facilitated seamless app development and distribution. This unification accelerated the growth of the , transforming it into a shared repository where developers could target multiple form factors with a single codebase, contributing to the ecosystem's expansion to over 2 million apps and more than 300 billion cumulative downloads as of 2025. Security support for iOS 4-compatible devices tapered off between 2012 and 2013, with the iPhone 3GS receiving its final major update to in September 2012, followed by a critical security patch in iOS 6.1.6 on February 21, 2014, to address vulnerabilities like those in SSL/TLS implementations. The iPhone 3G, limited to iOS 4.2.1 as its final version released in November 2010, lost all official updates shortly thereafter, marking the end of Apple's maintenance for the oldest supported hardware at the time. In the years since, legacy devices running iOS 4 have found niche applications among enthusiasts, primarily through jailbreaking tools like Legacy iOS Kit, which enable custom modifications, of outdated apps, and preservation of vintage software experiences on hardware such as the and 3GS. These devices are also emulated in development environments for testing legacy iOS behaviors or running historical apps in virtual setups, sustaining interest in iOS 4's era despite the lack of modern compatibility. The rollout of iOS 4's app switching and multitasking features intensified competition in the mobile OS space, prompting Android developers to refine their own interfaces, such as enhancing the recent apps overview for quicker transitions, in response to Apple's push toward more intuitive productivity tools.

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