Apple is expected to launch a new Apple Watch later this year (which you can read about here: Apple Watch 3 rumours), but the company is also updating the watchOS operating system software, bringing new features to existing Apple Watch models.

We got our first look at watchOS 4 at WWDC 2017 on 5 June. Read on to find out about all the new features.

Thinking of buying an Apple Watch? Read our Apple Watch buying guide 2017 and take a look at our guide to the best Apple Watch deals.

When will Apple release watchOS 4?

We saw a preview of watchOS 4 on 5 June at WWDC 2017. After the announcement, watchOS 4 went into a beta testing phase which will last for several months. It will finally become available for general download around September 2017.

However, if you're signed up as a beta tester you may be able to download an early beta version of watchOS 4 before then - possibly by the end of June 2017. When the software arrives, here's how to update watchOS.

watchOS 4 rumours: WWDC 2017

What's new in watchOS 4?

Here's a rundown of the new Apple Watch features we're going to get in the next version of the watch operating system.

Siri watchface

We're going to start with some new watch faces. Which might sound superficial - but it really isn't. At least this first one isn't.

A new 'Siri face' will display information personal to you using machine learning, similar to the proactive functionality and contact suggestions in iOS. (Which in our experience are okay but not spectacular, although these things are improving all the time.) Does this mean that Siri on the Watch is going to work when you're offline? Or can it work based entirely on the information available on-device?

watchOS 4 new features: Siri face

The Siri face displays information using machine learning, to match your routine - so you'll see the information and app shortcuts that are most relevant to your current needs.

You can rotate the Digital Crown to scroll vertically through the various notifications and apps on the face.

Other new faces

Apple also revealed two other groups of watch faces. First up is the kaleidoscope face, which you can rotate using the Digital Crown, producing a trippy effect. The visual elements rotate and change shape, just like those weird toys everybody apparently loved in the sixties.

watchOS 4 new features: Kaleidoscope face

There are also new Disney faces, following on from the popular Micky Mouse and Minnie Mouse faces already available. Woody, Jessie and Buzz Lightyear (from Toy Story) are all coming to the Apple Watch.

watchOS 4 new features: Toy Story watch faces

These seem to be a bit more advanced, visually speaking, than the previous faces. Mickey and Minnie were animated, but in a fairly limited way - jiggling back and forth in time with the clock, basically. But the new faces incorporate multiple, longer animations that behave differently each time you rotate your wrist. Apple called these 'vignettes' - the character climbing on to the watch face from below, for example.

Activity & Workout

Activity (and what we consider to be its companion app, Workout) are almost certainly the most popular apps on the watch. So we were pleased to see that Apple is continuing to tweak and add to these apps. As elsewhere, Apple is gradually increasing the influence of personalisation and machine learning.

The notifications in Activity are now more personalised to you - they'll let you know if you're close to an achievement, for example. And there's 'smart coaching', which again is personalised to you. This will offer monthly challenges, based on your history and activity records.

There's a cool new sparkly animation to celebrate filling your rings in Activity (it looks nice, but may pall after a few months...), and a change to the way pool swim workouts work. Apple says that taking a rest at one end of the pool will automatically be detected and be marked as the end of one set of laps and the beginning of another - handy for accurate timings.

We're really pleased to see Apple implement two-way data exchange with gym equipment. (The hopeless inaccuracy of treadmill-based workouts has long been an annoyance - when a device with a more accurate record is right there!)

watchOS 4 new features: Two-way data transfer in gyms

You simply need to tap the NFC tag to connect your watch with the gym equipment - although obviously you'll need to find a gym that supports it first. This is likely to take a while to filter out into the world outside California, we'd guess.

There's a new High Intensity Interval Training workout, which is great to hear. This is a demanding and highly effective form of workout that uses your heart rate to push you to your limits - we really enjoyed using this with the Moov HR Sweat activity tracker.

watchOS 4 new features: High Intensity Interval Training workout

Apple has also realised that notifications aren't important during a workout, so Do Not Disturb will automatically be activated when a workout is initiated. Of course, it'll also automatically turn it off once the workout is complete. 

Oh, and one last change to the Workout interface: you can swipe left from the workout menu to access music controls. (Why hasn't this been a feature from the beginning?)

Music

The Music app on Apple Watch has been redesigned, and looks much better than what we have at the moment. There's nice album art - you rotate the Digital Crown to scroll through.

(The Digital Crown seems to be getting far more use in watchOS 4 - which is great. It feels like an underused control in watchOS 3.)

The new Music app again tries to anticipate your needs - you'll automatically see music and playlists that you listen to regularly, freshly updated on your watch. It also includes Apple-curated playlists including the likes of Heavy Rotation, Favourites Mix and New Music Mix. Of course, you'll need an active Apple Music subscription to see these option. 

The Apple Watch also supports multiple playlists for the first time.

Other changes

There's a new, redesigned dock interface - you can vertically scroll through recent apps using the Digital Crown. (There it is again!)

There appears to be a new News app for watchOS, based on the watchOS 4 demo, but we haven't got any details. It might just be an interface redesign.

There's a new blinking light activated via Control Centre - useful for safety on night runs.

Apple claims you'll see faster app responsiveness and better background app performance.

You'll also be able to pay friends via Apple Pay on the Apple Watch via an Apple Pay Cash account, although it's initially limited to US users only. 

Finally, glucose monitoring is coming to the Apple Watch, although there's not much word on the companion hardware that will presumably be required.

We'll update this article as and when we hear more details.

Read about the Best Apple Watch games and Best Apple Watch apps for more information about what's currently available.

And for more information about the Apple Watch in general, read our Complete guide to the Apple Watch and our Apple Watch tips & secrets.