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This one catches almost everybody, and getting it wrong means confidently reading numbers from a device you did not intend.

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What hubs do

Apple Health — and on Android, Google Health and Health Connect — are hubs. Every device you own writes into them, and they merge it all together. That merging is the point. When you open Apple’s Health app and look at steps, you get your steps: your phone’s, your watch’s, and anything else, reconciled into one number. Convenient. And, for our purposes, destructive — because once merged you cannot tell what any individual device actually measured.

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What the Workbench does instead

It separates them again. When you connect Apple Health, the Workbench does not take the merged picture. It looks at what is inside and identifies which device each measurement came from — this sleep from the Watch, that sleep from the ring, those steps from the phone.
This is one of the main reasons the Workbench exists. Working out what a specific device provides is impossible from a merged number, and it is exactly what we need to know to design the finished app.

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Which means you may have to pick

If your hub contains data from more than one device, the app cannot know which you meant. So you may see a device list rather than just “Apple Health”, and you should pick the actual device.
1

Open Settings from the menu

2

Look at the three source pickers

3

If a picker lists devices rather than just a hub, choose the specific one

“Csanad’s Apple Watch”, not “Apple Health”. “Oura Ring”, not “Apple Health”.
4

Do it for all three, if they differ

See Choosing your sources.

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Why this matters more than it sounds

Two reasons. For you: if the app is reading your old watch, sitting in a drawer and occasionally syncing, your figures come from a device you are not wearing. That looks like the app being wrong, and it is really the source being unspecified. For us: if we cannot tell which device produced a night, that night tells us nothing about any device. Merged data would answer none of the questions we set out to answer.

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Devices you might not expect to see

  • Your iPhone. It counts steps and distance independently of any watch.
  • A device you no longer wear, if it still syncs occasionally.
  • Other health apps, if they write into Apple Health.
  • The same device twice, occasionally, if it has been re-paired or renamed.
If you see something you do not recognise, that is worth telling us about — it is precisely the kind of mess we want to find now rather than after launch.