My only remaining sleep tracker
I signed up for Sleep2 more than a year ago after reading their initial validation study. I work in health research, and we use Polars for data collection, so decided to try the app out. While it's not perfect, it's the best sleep tracker I have tried, mostly because I believe the data in their study, and virtually all other sleep trackers are very inaccurate. Literally, if you need better than 60% accuracy at a sleep stage level, there are no other consumer options. I would love to see additional validation data, but really they're the only option short of semi-clinical hardware.
I wore it while at a professional sleep study, as well. One night of data is insignificant compared to the number in their studies, but the data aligned quite well with the lab equipment. I also wore a Withings tracker, and that was quite poor.
I wish it had data export. This is my one big request. Sleep2 has been helpful and responsive via email, sending me my sleep data periodically by email, but it's cumbersome. I have a few additional tweaks in the UI that I'd love to see, but they are minor, and even with the export I believe I've found a way around this via Healthkit. The review right before this, with one star, is incorrect. After switching to the Polar Varity, the app has been rock solid. It does not drop your data easily. I use it nightly and have lost maybe two or three nights of data in the last year or two, max. It's a four star app in terms of design - good but with improvements - but it's five stars because I honestly believe it's the only meaningful consumer tracking app there is. That's much more important to me than UI placement.
I wore it while at a professional sleep study, as well. One night of data is insignificant compared to the number in their studies, but the data aligned quite well with the lab equipment. I also wore a Withings tracker, and that was quite poor.
I wish it had data export. This is my one big request. Sleep2 has been helpful and responsive via email, sending me my sleep data periodically by email, but it's cumbersome. I have a few additional tweaks in the UI that I'd love to see, but they are minor, and even with the export I believe I've found a way around this via Healthkit. The review right before this, with one star, is incorrect. After switching to the Polar Varity, the app has been rock solid. It does not drop your data easily. I use it nightly and have lost maybe two or three nights of data in the last year or two, max. It's a four star app in terms of design - good but with improvements - but it's five stars because I honestly believe it's the only meaningful consumer tracking app there is. That's much more important to me than UI placement.
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Worth The Price
I used both free version and Paid version
I would absolutely recommend the app because the Data presentation and The accuracy of the metrics is extremely good and It actually helped me become better at my sleep anxiety and sleep apnea
The support is actually very good and they are easy to contact if you have any query or any question regarding the app
I would absolutely recommend this app
I would absolutely recommend the app because the Data presentation and The accuracy of the metrics is extremely good and It actually helped me become better at my sleep anxiety and sleep apnea
The support is actually very good and they are easy to contact if you have any query or any question regarding the app
I would absolutely recommend this app
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Will Not Connect
Trying to connect with the Polar H10 is impossible even though my phone is connected and other apps don’t have issues connecting. Waste of time!
Connection issues
Could be a good app but I wouldn’t know. Connects to my polar H10 at night and I start sleep then when I wake up it can’t end my sleep or connect to my strap. Makes you delete the data.
Accurate stats
Sleep stats
Sleep scientists, not software developers
The app keeps surprising me with new bugs every day - losing my sleep data, not working well offline and a clumsy data entry UX. The sleep science might be solid but the app development skills are lacking. Hard to justify $20 per month for such a frustrating experience
Bugs
Constantly losing sleep sessions
Response from developer
Sorry to hear that, Villy_vonka! Losing sleep sessions is frustrating – but in most cases, there's a simple solution (e.g. the sensor is still connected to another app like Polar Flow). Just reach out to us at hello@sleep2.com – we’ll help you get it working smoothly again. Maybe you'll feel differently about the app once it’s all running properly?
Sehr hilfreich
Ich verwende seit einigen wochen sleep2 im intensive programm mit einem polar sensor und bin echt positiv überrascht. Jeden morgen bekommt man personalisiertes feedback mit verbesserungsvorschlägen für die nächste nacht und verschiedene übungen und lerneinheiten werden freigeschalten. Kann ich nur empfehlen!
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Incredibly pricey
Can you guys actually make it affordable lol. 15$ a month is crazy
App Crashed and No Data
After spending $500 on two H10 straps, you wake up to a closed app with no data. There is no way to recover your data in the app. Closing the app, repairing the sensor, and following the support documentation all failed. I should have checked the reviews before purchasing.
Very Accurate sleep data !
Connected with the polar h10 this is the best app for sleep tracking.
Response from developer
Thank you so much for your great feedback:) We are happy that you like the app & appreciate the precise sleep tracking with H10!
eingeschränkte track möglichkeit
Es sollte die Möglichkeit geben seinen Mittagsschlaf auch richtig zu tracken
Response from developer
Vielen Dank für die positive Bewertung und dein wertvolles Feedback! Wir freuen uns, dass dir die App gefällt und werden deinen Wunsch - den Mittagsschlaf zu tracken - bei zukünftigen Entwicklungen beachten!
Falsely Advertised
Paid for the PRO subscription, but it didn’t contain all of the metrics described. Additionally, the UI is quite poor for comparing data between nights and zooming into specific nightly data. And the final nail in the coffin resulting in cancelling subscription in under a week is no error detection or restart capabilities. I had nights where the device I wore (Polar H10) had a brief (5 second) Bluetooth signal loss, due to rolling onto my stomach while asleep. This resulted in Sleep2 ceasing all recording activity and dumping the ENTIRE night’s data.
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Good But Needs Improvement
This app, when paired with the Polar Verity Sense or Polar H10, provides what may be the most accurate consumer sleep tracking available. According to The Quantified Scientist on YouTube, the data quality is among the best — and from my experience, I trust the metrics it provides.
That said, the app experience itself holds it back.
First, as others have mentioned, the app occasionally freezes or fails to process the night’s recording — resulting in a complete loss of data. I’ve tried returning to the app multiple times over the past year hoping this issue had been resolved, but it still occurs. Losing an entire night of data is frustrating, especially when accuracy is the main reason for using it.
Second, the interface feels dated. It’s functional, but visually it looks retro — almost like something from the 1970s. A modern redesign would go a long way in improving the overall experience.
Third, the subscription price (around $19.99/month) feels steep given the stability issues. For an app at this price point, seamless data transfer and reliability should be expected.
Finally, it would be extremely helpful to allow multiple sleep sessions per calendar day. For those of us with fragmented sleep or irregular schedules, the current limitation makes tracking less practical.
In short, the sensor + app combination offers superior data compared to most other trackers. However, without consistent reliability and smoother usability, it’s fair to question whether it justifies the monthly subscription cost.
That said, the app experience itself holds it back.
First, as others have mentioned, the app occasionally freezes or fails to process the night’s recording — resulting in a complete loss of data. I’ve tried returning to the app multiple times over the past year hoping this issue had been resolved, but it still occurs. Losing an entire night of data is frustrating, especially when accuracy is the main reason for using it.
Second, the interface feels dated. It’s functional, but visually it looks retro — almost like something from the 1970s. A modern redesign would go a long way in improving the overall experience.
Third, the subscription price (around $19.99/month) feels steep given the stability issues. For an app at this price point, seamless data transfer and reliability should be expected.
Finally, it would be extremely helpful to allow multiple sleep sessions per calendar day. For those of us with fragmented sleep or irregular schedules, the current limitation makes tracking less practical.
In short, the sensor + app combination offers superior data compared to most other trackers. However, without consistent reliability and smoother usability, it’s fair to question whether it justifies the monthly subscription cost.
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Great insight
Everything works well. Heart rate tracking is clearly the best. Sense I’m using the polar h10. I don’t have a way to test the accuracy. However it does seem to be more accurate than my Apple Watch SE 2nd gen.
Very expensive and terrible with connecting to H10 Polar strap
It always gives me problems when connecting to the polar H 10 strap. The stress of always trying the different ways of resetting and repairing probably throws off the HRV readings anyway.
And it’s extremely overpriced. You probably would have a lot more people willing to pay if you lowered the price. Your profit would increase by more customers. I would expect seamless connections with my Bluetooth device as well.
And it’s extremely overpriced. You probably would have a lot more people willing to pay if you lowered the price. Your profit would increase by more customers. I would expect seamless connections with my Bluetooth device as well.
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Very expensive and needs some updating
The instructions about exporting data to Apple Health is outdated (there is no “more” section for this as stated in the FAQ). I think
In general the permissions are now different for Health integration.
And it’s extremely overpriced
In general the permissions are now different for Health integration.
And it’s extremely overpriced
Response from developer
Thank you for your feedback. You’re absolutely right - after a recent update, the former “More” section was renamed, and all related settings can now be found under “Profile”, including the Apple Health integration. We’re updating the FAQ accordingly to avoid further confusion. The basic version is available free of charge, while the added value lies in the paid version, which reflects the continuous development and scientific validation of our algorithms as well as the ongoing improvement of the app. If you have any questions, please feel free to contact us anytime at hello@sleep2.com - we’re always happy to help and clarify things directly.
Meine neue Lieblingsbeschäftigung
Ich nutze den Schlaftracker erst seit 2 Tagen. Ich bin ganz begeistert und mag ihn sehr. Er hilft mir, auf einen gesunden Lebensstil zu achten und die Übungen in Form von Audios, Video und Schlafcoach sind auch sehr interessant. Im Tagebuch kann man 300 Zeichen verwenden. Ich kann dort viel lesen und bekomme Tipps und kann zwischen zwei Programmen wechseln, mein Medizinprodukt basiert auf wissenschaftlichen Studien. Und ich kann Sleep2 kostenlos dank der TK für 12 Monate nutzen. Ich finde Sleep2 ganz toll.
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Response from developer
Hi LeoMaximilianNu - Vielen Dank für deine großartige Bewertung:) Wir wissen deine Rückmeldung sehr zu schätzen und freuen uns, wie begeistert du nach den ersten Tagen von sleep² bist! Besonders schön ist, dass dir sowohl die hochpräzise Schlafanalyse (Pro) als auch das Schlaftraining (Intensiv) einen echten Mehrwert bieten und du unseren wissenschaftlichen Hintergrund zu schätzen weißt! Super, dass du über die TK zwölf Monate lang kostenlos Zugang sleep² erhältst, freut uns ebenfalls. Wir wünschen dir weiterhin viele positive Erfahrungen auf deinem Weg zu einem gesunden und erholsamen Schlaf:) Wenn du mal Fragen hast oder Hilfe benötigst, melde dich gern jederzeit unter hello@sleep2.com bei uns
Overrated
The highest subscription, Pro, doesn’t provide enough sleep metrics. Compared to the free Coros app for Coros devices, Sleep2 is less user-friendly, easier to navigate, and less scientific. It lacks features like light sleep cycle duration. HRV data is not graphed, but heart rate can be graphed second by second. If a Coros app with an optical sensor watch can show an HRV graph, a scientific app developed by professors should do the same. The main reason for an ECG heart rate sensor is for many HRV data points. The Kubios HRV app for iPhone can show a second by second graph while taking a measurement and it doesn’t have paywalls, pretty deplorable for Nukkuaa that this is app exists.
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Room for improvement
When it works it works well but the app itself is pretty buggy. It is prone to getting hung perpetually on loading screens then dropping your data for the night when you try to reopen the app which is incredibly frustrating. Wish they would focus on a higher quality of code.
