iOS (iPhone Operating System) is the operating system that Apple’s iPhone runs on, and it’s at the core of the iPhone user experience. A system that’s as old as the iPhone itself it has gone through a number of changes over the years, with the latest version, the iOS 17, rolled out in 2023. Apple’s iOS operating system is one of the world’s most popular operating systems. Sleek, streamlined and convenient, Apple iOS’s main features include strong security, high-resolution displays and graphics, and an exclusive app store with more than two million choices.

Why is it important to know which version of iOS your Apple iPhone is running? There are a few reasons. Apple regularly releases iOS security updates to patch up vulnerabilities and protect your iPhone from the latest malware and bugs. Certain apps require the most up-to-date version of Apple’s iOS operating system in order to run properly. When you need support for your iPhone, knowing the iOS version makes it easier for the technicians to work out a solution.

If you’ve just bought a refurbished or second-hand iPhone, you might be wondering which version of iOS it’s running and whether the security and features are up to date. Luckily, it’s pretty easy to check and update your iOS when you need to. Here’s our brief guide to the history of iOS and which iPhones the various versions are compatible with.  

The Different iOS Versions

iOS has a long and detailed history with a variety of milestones. Here’s our rundown of the history of the Apple iOS operating system, starting at the beginning:

iOS 1

The earliest version of the operating system, released in 2007, came pre-installed on the very first iPhone. Originally called the iPhone OS, it lacked what would become some of Apple iOS’s main features, like third-party apps. But with exciting developments like Visual Voicemail and a multi-touch screen, it was revolutionary for its time.

iOS 2

After the roaring success of the debut iPhone model, Apple released the iOS 2.0 to go with the iPhone 3G. The most exciting new feature was the App Store and its support for third-party apps.

iOS 3

Released in 2010, this version of iOS was notable for being the first to support the iPad.

iOS 4

The iOS 4 introduced a number of new developments that would become Apple iOS's main features, including FaceTime and Multitasking.

iOS 5

With the iOS 5, Apple embraced the growing wireless trend by introducing iCloud and iMessage features. This was the last version of the iOS that Steve Jobs would see before he passed away in 2011.

iOS 6

Unravelled in 2012, this is the update that brought the world Siri, Apple Maps and Passbook (now called Wallet).

iOS 7

With the release of the iOS 7, Apple overhauled the entire user interface to make it more modern and introduced Touch ID, AirDrop and CarPlay.

iOS 8

2014’s iOS 8 was a huge update as far as new features go. It saw the introduction of the contactless Apple Pay payment system, Apple Music and iCloud Drive, among other features.

iOS 9

Released in 2015, the iOS 9 saw Apple focus heavily on speed, responsiveness, stability and performance, with new features including Night Shift and Low Power Mode.

iOS 10

Apple’s focus for the iOS 10 was customisation and connection. It allowed apps to communicate with and even borrow features from one another without the need to open a second app.

iOS 11

While iOS 11 was still an update for the iPhone, its focus was on the iPad—specifically, turning iPad Pro tablets into serious laptop replacements. The changes Apple introduced to make this happen included multiple workspaces, split-screen apps, and drop-and-drag support.