Fitbit has announced the Alta HR, adding to its already strong line-up of activity trackers. The new device sits into the company's "Everyday" category, alongside the original Alta and the Flex 2.

If you want to know which Fitbit is right for you, our separate feature helps explain them all, while this feature concentrates on the Alta HR, Alta and the Flex 2. Here are the differences and similarities between the three main everyday Fitbit devices.

  • Alta HR and Alta have interchangeable straps
  • Flex 2 is waterproof
  • Alta HR has more secure fastening

The Fitbit Alta HR and the Alta have very similar designs with a couple of differences that can only be seen from the underside of the device and when they aren't being worn. Both have a 1.4-inch OLED tap display at the top, a textured elastomer band as standard and a metal chamfered body. The straps are interchangeable and will work across both devices.

The Alta HR has a PurePulse heart rate monitor underneath the body and it switches the two-pin clasp found on the Fitbit Alta for a colour-matched buckle fastening that is a little more secure. Neither the Alta or Alta HR have waterproofing but they are both splash proof.

The Flex 2 is a removable tracker placed within a textured elastomer band that is also chamfered for a slightly more exciting look. The two-pin fastening is present again but rather than a display like the Alta, the Flex 2 opts for five LED lights that will each light up to display 20 per cent of a user's goal progress. The Flex 2 is also swim proof.

The Fitbit Alta HR, Alta and Flex 2 each come in four colours as standard, though not the same four. They can also all be customised. The Alta and Alta HR are customised with different straps, like leather, and there is also a solid bangle available for a smarter look, while the Flex 2's removable tracker can be placed within a range of accessories, including a pendant and bracelet.

  • Alta HR offers heart rate monitoring 
  • Alta HR offers more advanced sleep tracking thanks to HR racking
  • Flex 2 has swim tracking

The Fitbit Alta HR, Alta and Flex 2 all track steps taken, distance travelled, active minutes and calories burned. They also all track sleep, though the data collected will be more advanced on the Alta HR, with Fitbit introducing light sleep, deep sleep and REM sleep tracking on the new device.

The three devices also have Reminders to Move, Silent Alarms and Fitbit's SmartTrack feature, which will automatically recognise and track activities such as running, sports and aerobic activities, showing a summary in the app.

On top of these features, the Alta HR will also track heart rate monitoring, as we mentioned. This will mean the Alta HR will present more data for exercise, as well as offer more accurate calories burned data as it will more aware of how hard you are working. The Flex 2 however, offers swim tracking which neither the Alta or Alta HR can.

All three devices also offer smartphone notifications, in the form of text, calls and calendar alerts. The Alta and Alta HR both show the name of the caller, or the name and a scrolling message on their displays, while the Flex 2 alerts the user in the form of different coloured LEDs and a vibration as it has no display. Different colours signify a different alert, for example, a purple LED is a text message, while blue is a call.

The Alta and Flex 2 are both claimed to have a five-day battery life, while the Alta HR is claimed to bump this up to seven.

  • Alta HR is most expensive
  • Flex 2 is cheapest
  • Accessories and straps all cost extra

The Fitbit Alta HR is the most expensive, starting at £129.99. The Fitbit Alta sits in the middle, starting at £99.99, while the Flex 2 is the cheapest, starting at £69.99.

There are special edition Alta and Alta HR models that feature different coloured metal bodies and cost a little more, and all the accessories and straps for all the devices are also sold separately.

All three of the devices being compared here are slim, subtle and they all have the option of being customised for a smarter look.

The choice between them will come down to what you want from your activity tracker. The Fitbit Alta HR is the most advanced in terms of features thanks to the addition of heart rate tracking, but swimmers will want the Flex 2 as it is the only Fitbit device to offer waterproofing, for example.

We would certainly choose the Alta HR over the Alta given it offers more features in the same sized device, but the Flex 2 is only just over half the price and for some, the basic tracking it offers will be plenty.