Extensions are one of the most exciting aspects of Apple's iOS 8 operating system for iPad and iPhone. With extensions, apps don't just offer you features - they extend the features found in other apps. Learning how to install extensions can make your iPhone or iPad more powerful than ever.

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With extensions installed the Photos app can perform all new image-editing techniques, and Safari can access passwords stored in the 1Password app; and you can completely change the keyboard used across the system. It can be fairly tricky to get your head around extensions, and the idea of customising iOS itself is a bit new. It has been brilliantly implemented in iOS 8, though, and this feature looks at the different types of extension available and how to activate them.

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There are six different types of extensions that developers can create for iOS apps.

Share extensions in iOS 8

These extensions appear when you tap the Share icon in an iOS 8. It enables you to add new services, such as Pinterest, to the default ones such as Messages, Mail, Twitter and Facebook.

Share and Action extensions in iOS 8

Action extensions in iOS 8

This is a vague type. According to Apple, action extensions enable an app to "manipulate or view content originating in a host app". The 1Password app enables you to insert a password from 1Password into Safari, for example. The Actions extensions appear in the second line when you tap the Share icon in an App, next to default actions such as Copy and Print.

Photo Editing extensions in iOS 8

The Photos app has its own extensions system. If you install photo-editing apps with extensions, they can offer their functions directly inside Photos app. These extensions are accessed by tapping Edit on a Photo, and tapping the Photo Editors icon (a circle with three dots inside).

Photo editing extensions in iOS 8

Storage extensions in iOS 8

These extensions enable an app to access and manage a source of files across a range of apps. If a developer has several apps it can manage a shared storage area instead of each app having to store and share files. This will also enable services such as Dropbox, Google Drive and Microsoft OneDrive to introduce provider extensions for apps (making it easier for you to access files stored here). See: What you need to know about Apple iCloud Drive

Today / Notification Centre extensions in iOS 8

These are often referred to as widgets, but officially are known as "Today Extensions". These are the extension to the Notification Centre. Open Notification Centre > Today > Edit to access the available extensions.

Today extensions in iOS 8

Custom Keyboard

The final type of extension in iOS 8 is to add a third-party keyboard. Once installed they are accessed by tapping on the Languages icon on the iOS keyboard.

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How to add extensions to iOS 8

Extensions are added to iOS 8 along with apps. Even extensions that don't have any purpose other than to extend a feature in iOS 8 are installed as an app. If you want to add the Swype keyboard to iOS 8, you need to download the Swype app from the store. The app itself simply walks you through the process of turning on the extension.

Other extensions are turned on using the app that they extend. For example, in Safari, tap the Share icon to reveal two More icons (the top one is for Share and the bottom for Actions). Tap More to reveal a list of Share or Action extensions available (each has an On/Off switch). Setting the extension to On turns on the extension for that app. Its option will then appear as an icon in the Share list (which appears when you tap Share).

Safari extensions in iOS 8

Keyboards are added by first installing the Keyboard app from the App Store. Now tap on Settings > General > Keyboard > Keyboards > Add New Keyboard and pick the keyboard from the Third-Party Keyboards list. You can also choose to allow Full Access for each keyboard (which shares key press information with the keyboard maker but enables them to offer better predictive text and other functions). Tap on the keyboard in Keyboards list and set Allow Full Access to On.

Photos work slightly differently. Add an image-editing app, such as Camera360 from the App Store, and open the Photos app. Open an image and tap Edit > Photo Editors > More. A list of apps offering photo extensions will appear; tap the ones you want to On. Now tap Edit > Photo Editors and pick the app from the list of extensions. The features offered by the app will appear in the Photos app, and any effects you add are saved to the photo inside Photos.