Check head orientation with headphones

What this measures, and what it does not

Motion-capable AirPods report how your head is tilted relative to the ground. That is the whole of the signal: head pitch, and nothing below your head.

It is not a neck angle, and it is not a measure of your spine. Head orientation is research-grade — the kind of signal that shows how a working session drifts against your own usual range, and not a clinical reading of anything. Nothing here diagnoses a condition or tells you what to do about one.

The camera check is the path that estimates neck flexion and torso lean, and the two are kept as separate readings with their own labels and confidence. They are never fused into one posture score, and a head-orientation figure is never filed as a neck angle — not in what you are shown, and not in what is written down.

Set it up on iPhone

Open the posture coach and use Set up AirPods on the AirPods head orientation card. Setup asks for Motion access, then walks you through one calibration: sit the way you consider upright and save that as your neutral, with a live gauge showing the head pitch it is reading while you do it. The point of saving your own neutral is that head orientation is read against it rather than against somebody's idea of an ideal posture.

The live gauge exists so you can confirm tracking is working. What it shows is on-device and momentary — it is never stored, synced, or exported.

Calibrating does not start collection. Saving your neutral is groundwork: it records what upright means for you, and it turns nothing on. No head-orientation data is recorded while you work because you calibrated.

Recording is a separate choice, and it is off until you make it. The AirPods setup screen carries its own control — Record head orientation — beside the calibration gauge. It is off by default, turning it on is the only thing that activates recording, and turning it off again in the same place is how you undo that. If you have already calibrated, you are not opted in: an existing neutral is never read as agreement to be recorded, and nothing was switched on behind you.

That choice belongs to your account rather than to the phone. On a shared iPhone, turning it on for yourself does not turn it on for anyone else who signs in, and signing in does not inherit whatever the previous account chose.

When it records

A window opens when you come to the app. With Record head orientation on and a neutral saved, opening Achetrace — or returning to it — starts one sampling window of up to 30 minutes. It samples only while Achetrace stays open on screen, and only when Apple Health says you have been sitting still — the Apple Health article explains what that reads. Once a window finishes, nothing starts again until you next come back to the app. Nothing samples in the background, and nothing runs on a schedule.

Leaving the app ends the window early. What was observed up to that moment is kept as a shorter summary, as long as it saw enough slouched time to record, and the rest of the 30 minutes is not counted as observed.

Turning Record head orientation off stops a window that is running, and keeps nothing from it. Signing in as a different account does the same. Until late September 2026 there was one exception: a summary that had already finished and started uploading when you turned it off was kept. There is no exception now: a summary still being saved or uploaded when you turn it off leaves your readings and is not uploaded again, whatever stage it had reached. Before its upload starts, or after an upload that was refused, it is deleted. If it was uploading at that moment, it is removed from this iPhone and retracted from your account, and a retraction that fails stays queued and is tried again. If its upload failed, it is removed from your readings; when that upload had been queued for a retry, a copy is held on this iPhone solely so that its retraction can be sent if the upload did reach your account, and that copy is never uploaded. A summary that finished uploading before you turned recording off stays, like any other already recorded. If the new account has turned recording on for itself, a window opens for it against its own neutral; if it has not, nothing opens.

A saved neutral alone starts nothing. Calibrating while recording is off records nothing. If recording is already on, saving your first neutral opens a window; calibrating again while a window is running does not restart it — the new neutral applies from the next window.

Headphones are connected and nothing is captured

The first things to check are the two above: that Record head orientation is on for the account you are signed in as, and that a neutral is saved. A window also opens only when you come to the app, so one that has already finished waits for your next return.

When a window opens and cannot sample, the posture status says why rather than staying quiet. Apple Health may not be connected in this session, or may have nothing recent that says you have been sitting; the phone's battery may be too low; you may need to sign in so the summary can sync; or Motion access may be off. A window that sampled cleanly and found too little slouched time says so too, and records nothing.

The other reason shows up during setup rather than after it. Not every pair reports motion. The path needs motion-capable AirPods that expose head motion to the phone, and setup says so plainly when the connected pair does not. No later step changes that.

Whatever the reason, nothing else is waiting on this. Camera checks, manual posture and every logging flow work exactly as they do without AirPods.

Why this is not on Android

There is no head-orientation path on Android, and this is a settled boundary rather than a feature that has not arrived yet.

Android exposes no app-level head-motion interface. Earbuds report to the audio spatializer, which is a sound feature, and no public interface hands an app the head pose behind it. So there is nothing for Achetrace to read, on any handset and with any headphones.

Android therefore shows this as a named unavailable state and offers no setup to start — deliberately, because a setup path that cannot finish is worse than a plain no. Posture on Android comes from Check posture now and from Log posture manually, and neither of them is affected by this.

What is kept

On the iPhone, your neutral and your choice. Calibration stores the upright neutral you saved, in degrees. Alongside it, the app stores whether you turned Record head orientation on — a single on/off value, saved when you change it so the choice survives closing the app. Both are held on the iPhone against your account, so another account signing in on the same phone reads neither. Neither setting is synced, exported, or sent to the anonymous population data set, though each window that records keeps a copy of the neutral it was read against, as described below. The live gauge you watched while saving your neutral is momentary and is kept nowhere at all.

The raw motion stream is never kept. It is reduced on the phone as it arrives and discarded, so it is never stored, never synced, never exported, and never sent to the anonymous population data set.

Each window that records keeps one summary. It holds your mean forward head tilt against your neutral, the share of the window that read as slouched, how long the window ran, how much of that time was actually observed, that the reading came from headphones, and a caveat saying what headphone motion can and cannot see. It also holds how many of the observed minutes fell in each forward-tilt range — under 10°, 10° to under 20°, 20° to under 30°, and 30° or more beyond your neutral — together with the neutral those ranges were measured from, so a later recalibration does not change what an earlier window meant. These minutes go into your account and your personal archive export, and never to the anonymous population data set. Nothing you share with a clinician shows one window's minutes on its own, but a physical-therapy report you prepare, and any share link to it, can show their totals across the headphone sessions that report already includes. The summary is saved on the iPhone and shown with your other posture readings, and it reaches your account once its upload succeeds. The iPhone retries a failed upload only when the diary on this iPhone belongs to an account. Then, if the upload fails — because the phone is offline, for example — the posture status says it uploads when sync is back, and the iPhone tries again the next time you open the app or return to it while signed in to the same account. Until then it is on this iPhone only, so it will not appear after a reinstall or on another device. Two uploads are never retried, and for both the status says the cloud sync failed and the summary stays on this iPhone: one refused because a different account is signed in than the one this iPhone's diary belongs to, and one from a diary that belongs to no account, because the app was opened signed out.

It carries no neck angle and no torso angle. Head motion cannot observe either one, so the summary holds no figure for them and says in as many words that they were not measured — rather than a zero, which would read as a straight neck and an upright back that nothing here ever saw.

To delete them, open the Privacy tab on iPhone and tap Delete AirPods posture under Posture data. After you confirm, every head-orientation summary is removed from this iPhone and, when you are signed in, from your account, so a reinstall does not bring them back. If you are not signed in, they are removed from this iPhone only and the screen says so; if your account could not be reached, it says that instead, and tapping the button again retries. The delete covers all of them at once — there is no way yet to remove a single summary. Running setup again replaces the neutral with a new one, and turning the setting off stops new windows; neither removes a summary already recorded.