iOS 8, the next version of Apple's iOS operating system software for iPhone, iPad and iPod touch, is expected to launch alongside the iPhone 6 and iPad 6 in September or October. But a series of preliminary versions of iOS 8 - beta versions, for testing and optimisation work by app developers - have been released to those who’ve signed up to the beta programme.

In this article we'll look at the various beta versions of iOS 8 that have been launched so far, and at the beta versions still to come. We'll discuss the tweaks and fixes added in each iOS 8 beta, and the new features and design elements that have been added.

We look at these in reverse chronological order, so that the most recent/newest iOS 8 betas come first.

iOS 8 beta version 6: Launch date

iOS 8 beta 6 was the last beta before iOS 8 launches to the public on 17 September 2014. Fairly obviously, we expect beta 6 to be very close to the finished product (unless something goes drastically wrong!).

iOS 8 beta 6 was seeded to carrier testing partners on 18 August, but developers and other beta testers didn't get access. But don't worry too much - it contains only relatively minor big fixes, listed here by BGR.

If you want to join the beta programme and get access to iOS a few days before the general public, take a look at our article: How to join the iOS 8 beta

iOS 8 beta version 5: Features and design updates

iOS 8 beta 5 was seeded to testers on the 4th of August.

The iOS keyboard gained an easy-access switch to let you toggle iOS 8's QuickType predictive text feature on or off. Instead of having to go into the Settings app, you simply hold down the International keyboards button and slide the green button to go to non-predictve typing.

There's a new setting in the Health app that makes your health ID information available on the lock screen - a potential lifesaver if you have a long-term condition in need of medication.

And there are some cosmetic tweaks, too, with some changes to the iCloud app icons to make them seem like more of a coherent group. The icons are all a blue cloud on a white background, each sporting a different white icon in the middle.

iOS 8 beta version 4: Features and design updates

iOS 8 beta 4 fixes many of the large number of bugs found in beta 3.

For example, it had been reported that "swiping or tapping a Game Center friend request notification anywhere automatically accepts the friend request" - this is now fixed. Apple has also dealt with an issue that caused the Messages app to periodically become unresponsive if you have Send As SMS enabled in the settings, and another that was creating duplicate images in Photos if both iCloud Photos and Photo Stream are enabled; Siri’s ‘Hey Siri’ activation command has been tweaked to make it less likely to fail.

On the features front, iOS 8 beta 4 removes the Bug Reporter app that was present in iOS 8 beta 3 ("We've received wonderful feedback on previous betas via the Bug Reporter app. Thank you! However, this app has been removed in beta 4."), adds a Display and Brightness Settings menu (and new settings to customise swipe actions), and entirely alters the look of Control Center.

But these all pale next to the two most appealing additions in iOS 8 beta 4: a Suggested App feature, and a new Tips app.

iOS 8 beta version 3: Features and design updates

iOS 8 beta 3, which was released on 7 July, featured some minor tweaks to the previous version. These included a toggle to switch QuickType on or off, a new wallpaper (a grey/white gradient), changes to the way information is presented in the Weather app, and updated settings for Handoff and iCloud Drive. The Health app can now track your movement (steps, etc) using the M7 co-processor in the most recent generation of iDevices. Many users also reported that it felt faster than beta 2. Oh, and Shared Photo Streams were renamed to Shared Albums.

Beta 3 also included a long list of fixes. Perhaps the most interesting was that previously the feature in Family Sharing whereby a youngster could ask permission from the credit card holder to download a piece of content hadn’t really worked - it was apparently possible, among other issues, for the requester to approve their own request. That’s now been fixed.

(It still seemed to be a work in progress at this point, however - it remained impossible to create accounts for under 13s, previously purchased family content is only free to redownload if you download from the Purchased page, rather than the store page itself, and "a blank screen may be seen after creating a family on iPad".)

iOS 8 beta version 2: Features and design updates

iOS 8 beta 2 saw various updates on the initial version. The Podcasts app was made a mandatory pre-install, just as iBooks had been in the first beta (this means you don’t need to install Podcasts or iBooks any more, but you can’t delete them from your device if you don’t like them). And Safari gained an auto-blocking feature to prevent adverts on web pages pushing the user to the App Store.

QuickType, the promising and eerie-looking predictive keyboard system unveiled at WWDC but only previously made available for the iPhone, was rolled out to iPads with iOS 8 beta 2.

Beta 2 also saw some minor cosmetic tweaks - some buttons in Messages switched from blue to grey - and like all the beta versions above, beta 2 included a number of fixes to address problems encountered by testers. One of the more noteworthy dealt with crashes that sometimes happened when users installed third-party keyboards.

iOS 8 beta version 1: Features and design updates

This was the preliminary version of iOS 8 showcased at WWDC 2014. While visually it's hardly changed at all, iOS 8 beta 1 offers many new features (and significant tweaks too existing features) to set itself apart from iOS 7. To read all about iOS 8's features and design changes, check out our iOS 8 preview, or read our iOS 8 FAQs article from the launch night.

Read more:

iOS 8 preview

iOS 8 extensions wishlist: 6 iOS 8 apps we hope will work together thanks to Apple's new extensions

How to get iOS 8 on your iPhone and iPad right now

How to get iOS 8-like apps for Time-lapse now

Why Apple opened up: iOS 8 and Tim Cook's new era

Open sesame: How iOS 8 will unlock Touch ID's power

Apple's new iOS 7 beta 5 includes more design tweaks, extra features and new improvements