# sleep² sleeptracker & analysis — user reviews

> 53 indexed App Store user reviews of sleep² sleeptracker & analysis by Nukkuaa, rated 3.40/5 from 34 ratings.

- Source: https://appshunter.io/ios/app/sleep-sleeptracker-and-analysis/id1629426238/reviews
- App overview in markdown: https://appshunter.io/ios/app/sleep-sleeptracker-and-analysis/id1629426238.md
- Rating breakdown: 5★ 16 · 4★ 2 · 3★ 3 · 2★ 7 · 1★ 6

## Newest reviews (11 of 53)

### 2/5 — Will Not Connect

*2026-06-17, version 3.6.16*

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!

### 4/5 — Bugs

*2026-04-25*

Constantly losing sleep sessions

**Developer response:** 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?

### 4/5 — eingeschränkte track möglichkeit

*2026-02-23*

Es sollte die Möglichkeit geben seinen Mittagsschlaf auch richtig zu tracken

**Developer response:** 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!

### 3/5 — Good But Needs Improvement

*2026-02-22, version 3.5.0*

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.

### 2/5 — Very expensive and needs some updating

*2025-12-27*

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

**Developer response:** 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.

### 3/5 — Room for improvement

*2025-10-04, version 3.3.4*

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.

### 4/5 — Lots of potential

*2025-09-23*

I do believe their measurement accuracy - I just wish the offline UX was more refines

**Developer response:** Hi JohnJohn! Thanks so much for your trust in our measurement accuracy – we really appreciate it! 😊 We're continuously working on refining the user experience and your feedback is very valuable in that process. If you’d like to share specific suggestions, feel free to reach out to us at hello@sleep2.com .... we’d love to hear from you!

### 2/5 — So Overpriced

*2025-06-07, version 3.0.2*

Not worst it for 12 bucks per month. No free trial, i used this app only one day and switched back to sleepcycle.

### 4/5 — Bonne analyse du sommeil

*2025-05-09, version 3.0.2*

L’application est bien faite. J’aime le fait de me demander les questions au réveil pour comparer avec les données (combien demander temps pour m’endormir, combien de fois réveillé et combien de temps réveillé). Ça confronte notre perception du sommeil. La traduction en français de certains termes est parfois bizarre ainsi que les voix utilisées pour les capsules d’informations. La principale raison que je n’ai pas donné 5 étoiles est le prix de l’abonnement qui est trop cher selon moi.

### 3/5 — Keine Einschlafzeit

*2025-03-21*

Seit dem Update kann man nicht mehr manuell eingeben, wann man das Licht ausgemacht hat. So denkt die App, dass man immer sofort eingeschlafen ist, obwohl man manchmal 2 h gebraucht hat. Sehr schade! Zur Zeit speichert die App auch nicht meine Schlaffaktoren. Auch wenn ich sie nachträglich eingebe tritt irgendein Fehler auf und es wird nicht gespeichert. 
Die meisten Übungen/Meditationen finde ich persönlich nicht so gut, da die Stimme zu mechanisch klingt. Nutze diesen Part daher gar nicht mehr.

**Developer response:** Vielen Dank für Ihr Feedback! Es tut uns leid, dass aktuell mehrere Punkte nicht wie gewünscht funktionieren. Bitte schreiben Sie uns an hello@sleep2.com – wir schauen uns das im Detail an und helfen Ihnen gerne individuell weiter. Vielen Dank für Ihre Geduld!

### 5/5 — the most accurate sleep stage tracker

*2025-03-12, version 2.7.3*

this company has done the hard scientific work to prove that their algorithm is the best available with published studies on their website. customer support is very responsive to suggestions.

## Most critical reviews (10 lowest-rated)

### 1/5 — Connection issues

*2026-05-15, version 3.6.12*

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.

### 1/5 — Sleep scientists, not software developers

*2026-04-30, version 3.6.12*

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

### 1/5 — Incredibly pricey

*2026-03-24, version 3.6.6*

Can you guys actually make it affordable lol. 15$ a month is crazy

### 1/5 — App Crashed and No Data

*2026-02-26*

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.

### 1/5 — Falsely Advertised

*2026-02-22, version 3.5.0*

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.

### 1/5 — Very expensive and terrible with connecting to H10 Polar strap

*2026-01-11, version 3.5.0*

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.

### 1/5 — Overrated

*2025-10-14, version 3.3.4*

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.

### 1/5 — Unacceptable

*2025-08-07, version 3.2.1*

So if I go to bed, and get up because something happened. And then start tracking a couple of hours later, after the crisis has been averted, not deleting the previous session. Not only does it start tracking perfectly normally, not warning me of the impending doom. But I get the wonderful message first thing in the morning that all the data will be thrown out. No options, no solutions, just a rude message to wake up to.

### 1/5 — Connection to Polar H10 troublesome

*2025-05-30, version 3.0.2*

You constantly need to discard your overnight sleep data just so you can repair the lost Bluetooth connection.

### 1/5 — Not impressed

*2024-09-25, version 2.4.2*

App is very clunky. A lot of the data is the same and can be read on Apple health that is free. I attempted to use polar h10 sensor but always says there is an error with data. Other apps worked fine for sleeping. Not worth $22/month.

## Most praised reviews (10 highest-rated)

### 5/5 — My only remaining sleep tracker

*2026-08-05, version 3.6.18*

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.

### 5/5 — Worth The Price

*2026-07-02*

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

### 5/5 — Accurate stats

*2026-05-11, version 3.6.12*

Sleep stats

### 5/5 — Sehr hilfreich

*2026-04-24*

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!

### 5/5 — Very Accurate sleep data !

*2026-02-26*

Connected with the polar h10 this is the best app for sleep tracking.

**Developer response:** Thank you so much for your great feedback:) We are happy that you like the app & appreciate the precise sleep tracking with H10!

### 5/5 — Great insight

*2026-02-07, version 3.5.0*

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.

### 5/5 — Meine neue Lieblingsbeschäftigung

*2025-12-01*

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.

**Developer response:** 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

### 5/5 — Mehrwert

*2025-08-01*

Im Vergleich zu anderen Apps wo es (nur) viele Metriken gibt, merkt man dieser App an, dass sie von einem Team entwickelt wird, dass sich in ihrem Fachgebiet gut auskennt (und das auch belegen kann). Die Tipps jedenfalls bzgl. besserem Schlaf sind meines Erachtens jedenfalls wertvoll und bieten einen Mehrwert.

**Developer response:** Vielen lieben Dank für dieses großartige Feedback, fox800! Super, dass du den wissenschaftlichen Hintergrund von sleep² erkennst und unsere Empfehlungen als echten Mehrwert empfindest. Genau das ist unser Ziel:) Wir freuen uns, dass du mit dabei bist und hoffen, die kommenden Weiterentwicklungen gefallen dir genauso gut!

### 5/5 — Excellent. Better than whoop for sleep tracking

*2025-06-11, version 3.0.2*

I was a whoop user for years and recently decided to try and look for an app that could give me a better HRV reading than the Apple Watch — without costing as much as whoop. And this is it! The app is great when paired with a polar strap (I use the H10) and what I like
The most is the very direct feedback the app gives me every morning about which aspects of my sleep I need to Improve and how. 

I’ve tried other apps for this like garmin, whoop, gentle streak, and sleep cycle and this is by far the best one. Plus using a chest strap means I don’t have to charge another device to track my sleep. 

The only thing I wish they would change is to allow the app to write sleep data to the Apple health app through HealthKit. The app
Doesn’t current do this which means I still wear my Apple Watch to bed (huge bummer) bc the data in sleep2 stays only in the app itself. But I contacted support and they answered me (super fast!) and told that should change soon. 

Their support team seems great and I really appreciate how personable and detailed they were in their response to me. Excellent customer service.

### 5/5 — Gutes Schlaftracking

*2025-06-02*

Zusammen mit dem Polar Sense ergibt sich ein sehr gutes Schlaftracking. Die Schlafphasen werden dadurch wesentlich besser erfasst als mit Schlaf Apps ohne zusätzlichen Sensor.
Eine zusätzliche Weckfunktion und weitere Analysemöglichkeiten wären wünschenswert.

**Developer response:** Danke für dein positives Feedback. An einem Schlafphasen-Wecker arbeiten wir tatsächlich. Auch sind wir daran andere Features die User häufig wünschen zu entwickeln.

Aktuell sind wir an den Schlaffaktoren dran die wir abendlich in sleep² zwar abfragen, zu denen du aber aktuell noch keine Rückmeldungen erhältst. Verwende diese regelmäßig sodass du dieses kommende Feature bald nutzen kannst!

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-25.*