---
title: HKMetadataKeyAlgorithmVersion
framework: healthkit
role: symbol
role_heading: Global Variable
path: healthkit/hkmetadatakeyalgorithmversion
---

# HKMetadataKeyAlgorithmVersion

A key that indicates the version number of the algorithm used to calculate the sample’s value.

## Declaration

```swift
let HKMetadataKeyAlgorithmVersion: String
```

## Discussion

Discussion This key takes an NSNumber containing an NSInteger. note: In watchOS 8, the system uses this key for heartRateVariabilitySDNN and HKHeartbeatSeriesSample samples generated by Apple Watch.