Each generation of Apple Watch offers more powerful hardware and tweaks to the design. But the most significant upgrades to the feature set come via watchOS software updates, which are free - you just have to install them on your device.

In this article we look ahead to the next major watchOS update for 2019. We sift through the leaks and rumours to predict watchOS 6's release date and new features, and the Apple Watches which will be able to run it.

If you're interested in picking up a bargain while you wait for the update, have a look at our roundup of the best Apple Watch deals.

Release date

watchOS 6 will be announced and demonstrated at WWDC 2019 in June. A few days later a pre-release beta testing version will be made available for developers only (there has never been a public watchOS beta), and this will evolve through subsequent point updates leading up to the final public release in the autumn - probably September 2019.

This is a regular schedule and we're pretty confident about the timing. The last four watchOS updates have followed the pattern of a WWDC summer announcement followed by an autumn public launch. (watchOS 1 was preinstalled on the original Apple Watch, which came out in April, so doesn't quite fit.)

Which Apple Watches will get watchOS 6?

The Series 3 and Series 4 are both safe, and will be able to update to watchOS 6. And the Series 5, which we expect to launch at the same time, will have it preinstalled.

Things are less certain for the older models.

Our prediction is that the dear old Series 2 will be certified as compatible with watchOS 6 (although it may see a loss of performance on the new OS, if it's got a lot of demanding new features), while the Series 1 and its less powerful S1P chip will not. But Apple will be keen to offer wide compatibility if it thinks the hardware can cope.

The first-gen Apple Watch definitely won't get the new update. It isn't even allowed to run watchOS 5.

watchOS 6 release date: New features

New features

It's too early to be sure of the features Apple will cram into the watchOS 6 update, but every Apple Watch owner has a wish list of capabilities they hope will be included. Here's what we want from watchOS 6.

Multi-user competitions

Obviously all competitions are multi-user, but we mean more than two, which is the arbitrary-feeling limit for Activity competitions at present.

As marvellously motivational as we find this feature (here's how to win Activity competitions), it could only be improved by allowing more people to join in, and thus a higher level of difficulty. Occasionally we find that we can relax in the latter half of the week because our opponent has fallen so far behind, but with three opponents, say, this would be much less likely to happen.

Allowing more entrants would mean minor tweaks to the scorekeeping interface, and slightly larger ones to the way challenges work, but feels straightforward to implement.

Always-on display

This is one of the most requested features of the Apple Watch. It seems preposterous for a watch not to even offer the option to always be displaying the time.

The decision not to have an always-on watch face was made in order to preserve battery life, and that is sensible... for most users. But plenty of rival smartwatches do offer this feature - sometimes compromising with a simplified or monochrome 'sleeping' face - and few things are as frustrating as trying to jog your wrist to wake up your watch and see the time, and failing. Surely there is a way around this.

Face ID

The way Apple rumours often work is that a feature appears on one of the company's products and then everyone predicts that the same feature will then appear on all of the others. Hence the rumours of iPhones getting Digital Crown dials and Apple Pencil compatibility, or of everything that isn't an iPhone getting Face ID.

Admittedly the Face ID one turned out to be true for the 2018 iPad Pro models. But it feels like the technical issues would be more difficult in bringing this feature to a watch.

watchOS 5 release date & new features rumours: Face ID

Could Face ID work on the Apple Watch? It seems like a long shot: at the moment the device doesn't even have a camera. But it is consistently (if wishfully, in our view) rumoured that a future Apple Watch model will get a FaceTime camera, and this could be combined with the necessary array of sensors that Face ID requires.

So much for the means. But what about motive?

The Apple Watch has far less need of a biometric unlocking tech than the iPhone and iPad. Apple Watches don't have Touch ID; you just unlock them with a code when you put them on in the morning (or even bypass this by putting on the watch and then unlocking the paired iPhone). The Face ID sensors would be used for unlocking purposes once a day, and Animoji, and that hardly justifies the inclusion of a lot of expensive high-end tech.

Sleep tracking

Many fitness trackers and smartwatches feature sleep tracking functions that monitor your movement while asleep and offer stats and analysis when you wake up - a feature that up until now has been missing from the Apple Watch (other than in the form of third-party apps).

Not for much longer, though, if a report is to be believed. Bloomberg claims that Apple is working on a new app that tracks a user's sleep. Apparently this feature will be supported across all existing models of Apple Watch.

The problem here has always been that sleep tracking required the watch to have enough charge to be used overnight. The Series 2 has two-day battery life, but other models offer less, and most watch users plug in their watch overnight, every night.

One saving grace is that it doesn't take long for the Apple Watch to charge, so owners keen to track their sleep could charge the watch during the evening before bed, for example.

In the meantime, get a good night's sleep with our guide to the best iPhone sleep apps.

New Apple Watch apps

The range of third-party apps available is constantly growing, but even after the announced support for Podcasts in watchOS 5 there remain a couple of Apple's own iOS apps that we'd love to get on the Watch.

First up: the Notes app. While it's unlikely you'll be writing (or even dictating) long notes on the Apple Watch, it would be useful to be able to access your existing Notes on that device.

If you're like us, Notes tends to be a go-to for any piece of information you want to have at your fingertips, so having access to this on your watch could be useful.

And our second pick is the Calculator app, which would be super-handy to have access to without taking out a phone, especially if made available from the Control Centre. (A third-party alternative at the moment is CalcBot, but Apple ought to be catering for these requirements itself, considering that it has a calculator app.)

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

More randomised watch faces

We love the Toy Story animated watch faces added in watchOS 4 (which are far more interesting than the near-static Mickey and Minnie faces), but what we particularly love is the Toy Box option. Instead of picking which character you want, this makes the watch display a randomly chosen character (and animated scene) each time you raise your wrist.

watchOS 6 release date & new features rumours: Toy Box

Apple has extended this concept to other faces - similar effects are possible with the Photos and Vapour faces - but we'd like more. The time-lapse photos of city skylines are good but we get bored of always seeing the same one, so a randomised selection would be an improvement. Same for Kaleidoscope.