Here's what you need to know about the iOS 8 update, it's new features and whether you should upgrade your iDevice. Updated on 16/10/14. See how to upgrade to iOS 8.

Update: Apple has announced that iOS 8.1 will be available to download for free on Monday 20 October.

iOS 8 compatibility

With the launch of the iPhone 6 and iPhone 6 Plus, Apple launched iOS 8 for free on 17 September. Relive our live coverage of the iOS 8 launch - see How to watch the iPhone 6 launch live and New iPhone 6 live blog: Plus 2014 Apple iPhone Air, iOS 8, iWatch launch as it happened.

iOS 8

"iOS 8 will be available this fall as a free software update for iPhone 4s, iPhone 5, iPhone 5c, iPhone 5s, iPod touch 5th generation, iPad 2, iPad with Retina display, iPad Air, iPad mini and iPad mini with Retina display," says Apple.

iOS 8 features: new features and apps

For more in-depth information on the new features, see our iOS 8 review

iOS 8 builds on the design of iOS 7. iOS 7 wasn't recieved well by everyone, though. The redesigned interface wasn’t universally popular and some of the low-contrast elements caused problems for some people with impaired sight.

Meanwhile, Apple refers to iOS 8 as "the biggest release since the launch of the App Store, giving users incredible new features and developers the tools they need to create amazing new apps".

"iOS 8 offers simpler, faster and more intuitive ways to use your device with incredible new features like iCloud Photo Library, a new Messages app, the QuickType keyboard and an entirely new Health app," said Apple's senior VP of Software Engineering Craig Federighi. "We're also giving developers amazing new tools to make managing your health and your home from your devices an integrated, simple and secure experience."

As expected, Apple has unveiled a new health and fitness app, which is actually called 'Health' and the accompanying 'HealthKit' rather than 'Healthbook' as originally anticipated. The Health app can monitor all of the metrics you're most interested in using third-party apps, too.  The Health app gathers info from your various fitness trackers and gadgets - with your permission - then puts all those stats in a single interface. So, for example, you could pull in sleep and nutrition info to build a complete picture. Apple is working with leaders in healthcare apps such as Epic Systems. See also: Can your iPhone replace your doctor?

No current iPhone has sensors that can monitor heart rate, blood pressure and other such metrics. The iPhone 6 can't either but it can with companion hardware such as  the Apple Watch and third-party gadgets.

iOS 8 Health

iCloud Photo Library lets you access your photos and videos on any device. The Photos app offers smart editing tools or you can access individual tools for deeper fine-tuning. Every adjustment is replicated on all your devices.

iCloud Photo Library smart editing  iOS 8 photos

Family Sharing is also a new feature in iOS 8. You can now set up your family on their iOS devices (up to six members with individual Apple IDs are supported), and get automatic photo stream, calendars, reminder lists and Find My Friends. You can also share purchases with every member of your family, too. This will work for up to six family members sharing the same credit card.

iOS 8 Family Sharing

Plus, if your child wants to download something onto their device, you'll get a notification on your device asking for your permission.

iOS 8 app permission

iOS 8 also has a refined Notification Centre, which includes extremely welcome Interactive Notifications. You can now reply from messages right from where you are by pulling down on the Notification Centre.

This works on the lock screen too. You'll get action buttons to enable you to deal with the Notification right there.

ios 8 Notifications

iCloud Drive allows you to store, access and edit documents across your devices. Any revisions will immediately be available on your other devices.

iOS 8 gives you quick double-tap access to get to frequently accessed contacts.

Managing your emails is easier in iOS 8, too. You'll be able to mark as unread, flag emails and delete easier with swipes. Tap to talk lets you share your voice, too. You'll also be able to access something else in your inbox while you're composing an email. Group messaging lets you talk to several contacts at once, and you can share photos, videos and your current location.

iOS 8 Messages

Other elements that have been tweaked include the Spotlight/Search feature, the Keyboard (with a new quicker way to type, aptly called QuickType) and Messages. The QuickType keyboard, for instance, supports predictive typing and can take context - such as the recipient - into account. It can suggest your favourite phrases, allowing you to write a sentence in a couple of taps.

See also: The 24 best smartphones of 2014