Wearable guides
Withings ScanWatch 2: PPG Sensor
ScanWatch 2 is a hybrid analog watch. Withings lists ECG, SpO2 and temperature tracking, 5 ATM water resistance, and about 30 days per charge. The photograph is the 42 mm black ScanWatch 2.
Withings lists ECG, SpO2 and temperature tracking on ScanWatch 2, with 5 ATM water resistance (Withings: ScanWatch 2). Withings says the watch is designed to run 30 days per charge in its sample usage scenario, and that frequent SpO2, ECG and workouts shorten that (Withings Support: ScanWatch 2 battery).
The photograph is the 42 mm black ScanWatch 2. This guide does not add accuracy figures. Published rows in the evidence table name the model that was tested. Several of those rows are the original ScanWatch, not ScanWatch 2.
Sourced figures
Every number in this guide comes from the source linked beside it. Each study result applies to that study's devices, participants and protocol only.
Withings ScanWatch 2 manufacturer specifications: ECG, SpO2 and temperature tracking; 5 ATM water resistance.
Withings says ScanWatch 2 is designed to run 30 days per charge in its sample usage scenario; frequent SpO2, ECG and workouts shorten it.
What published studies show
Results quoted from 7 published validation studies, each against a clinical reference. A result applies to the model and protocol tested, not to every model the brand sells. From the wearable accuracy database (v1.0.0).
Heart rate at rest1 study
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Withings ScanWatch | MAPE < 10% in all domains except shopping (10.8%); < 5% when sedentaryStudy finding (no single number) | ECG chest strap (Polar H7/ | n = 7, 12-h free-living | Giggins et al. (2022)Independent |
- Withings ScanWatchMAPE < 10% in all domains except shopping (10.8%); < 5% when sedentary
Study finding (no single number) · vs ECG chest strap (Polar H7/H10) · n = 7, 12-h free-living
Giggins et al. (2022) Independent
Heart rate during exercise1 study
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Withings Pulse HR | Good at rest and 2.7 km/h (r ≥ 0.82); poor at higher speeds (r ≤ 0.33)Study finding (no single number) | ECG chest strap (Zephyr BioHarness / | n = 22, Sitting, standing, Bruce treadmill stages 1–4 | Mendt et al. (2025)Independent |
- Withings Pulse HRGood at rest and 2.7 km/h (r ≥ 0.82); poor at higher speeds (r ≤ 0.33)
Study finding (no single number) · vs ECG chest strap (Zephyr BioHarness / Faros) · n = 22, Sitting, standing, Bruce treadmill stages 1–4
Mendt et al. (2025) Independent
Sleep stages (4-stage)1 study
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Withings ScanWatch | κ = 0.22Cohen's kappa | Polysomnography (PSG) | n = 41, Sleep laboratory, 1 night | Schyvens et al. (2025)Funding not reported |
- Withings ScanWatchκ = 0.22
Cohen's kappa · vs Polysomnography (PSG) · n = 41, Sleep laboratory, 1 night
Schyvens et al. (2025) Funding not reported
Sleep vs wake (2-stage)1 study
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Withings ScanWatch | > 90% (all devices)Sensitivity | Polysomnography (PSG) | n = 62, Sleep laboratory, 1 night | Schyvens et al. (2025)Funding not reported |
- Withings ScanWatch> 90% (all devices)
Sensitivity · vs Polysomnography (PSG) · n = 62, Sleep laboratory, 1 night
Schyvens et al. (2025) Funding not reported
Blood oxygen (SpO2)3 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Withings ScanWatch | Highest missingness: 69.5% of attempts successfulStudy finding (no single number) | Medical-grade pulse oximeter | n = 49, Spot readings, with and without chronic pulmonary disease | Jiang et al. (2023)Independent |
| Withings ScanWatch | Met ISO RMS ≤ 4% at normoxia and SpO2 < 90%Study finding (no single number) | Medical-grade pulse oximeter | n = 18, Induced hypoxemia (FiO2 14%, 12%, 10%), ISO 80601-2-61 | Walzel et al. (2023)Independent |
| Withings ScanWatchdetecting clinically significant hypoxia | 68.5% (spec 80.8%)Sensitivity | Medical-grade pulse oximeter | n = 200, Hospital ward, COVID-19 inpatients | Rajakariar et al. (2024)Independent |
- Withings ScanWatchHighest missingness: 69.5% of attempts successful
Study finding (no single number) · vs Medical-grade pulse oximeter · n = 49, Spot readings, with and without chronic pulmonary disease
Jiang et al. (2023) Independent
- Withings ScanWatchMet ISO RMS ≤ 4% at normoxia and SpO2 < 90%
Study finding (no single number) · vs Medical-grade pulse oximeter · n = 18, Induced hypoxemia (FiO2 14%, 12%, 10%), ISO 80601-2-61
Walzel et al. (2023) Independent
- Withings ScanWatch68.5% (spec 80.8%)
Sensitivity, detecting clinically significant hypoxia · vs Medical-grade pulse oximeter · n = 200, Hospital ward, COVID-19 inpatients
Rajakariar et al. (2024) Independent
Atrial fibrillation detection1 study
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Withings ScanWatchsmartwatch ECG app, inconclusive tracings counted | 58% (spec 75%)Sensitivity | 12-lead ECG | n = 201, Tertiary cardiology service, single-lead ECG algorithms | Mannhart et al. (2023)Funding not reported |
| Withings ScanWatchsmartwatch ECG app, inconclusive tracings counted | 75%Specificity | 12-lead ECG | n = 201, Tertiary cardiology service, single-lead ECG algorithms | Mannhart et al. (2023)Funding not reported |
- Withings ScanWatch58% (spec 75%)
Sensitivity, smartwatch ECG app, inconclusive tracings counted · vs 12-lead ECG · n = 201, Tertiary cardiology service, single-lead ECG algorithms
Mannhart et al. (2023) Funding not reported
Specificity, smartwatch ECG app, inconclusive tracings counted · vs 12-lead ECG · n = 201, Tertiary cardiology service, single-lead ECG algorithms
Mannhart et al. (2023) Funding not reported
Withings ScanWatch 2: PPG Sensor Comparisons
Frequently Asked Questions
Which watch is in the photograph?
Withings ScanWatch 2, 42 mm, black dial and black strap.
Do the evidence-table results apply to ScanWatch 2?
Only when the row says ScanWatch 2. Several published rows are the original ScanWatch.
Sources
- Withings. Withings ScanWatch 2 product specifications
- Withings. ScanWatch 2 battery life information