The short answer
Apple's foldable is widely reported to use Touch ID built into the side button rather than Face ID. Apple has not confirmed it — that comes on 9 September.
If it holds, it removes a design option most rugged cases rely on: the covered button. A sensor in the power button has to touch your actual finger, so the case must leave it open. That is a harder engineering problem than it sounds.
Most coverage treats this as a convenience story — Face ID versus a fingerprint. From a case design desk it is something else: a constraint that eliminates a whole category of product.
By Priya Nair · FoldifyCase foldable case design team · 3 September 2026
Why a side-button sensor is a case problem
Cases handle buttons one of two ways.
Covered buttons. The case moulds over the button in the same material and you press through it. Almost every rugged case does this, because an unbroken wall seals better, survives drops better and feels more solid.
Open cutouts. The case leaves a hole and you press the bare button. Slimmer cases often do this. Less protective, harder to make look deliberate.
A fingerprint sensor in the power button makes the first option impossible. Capacitive sensors read the ridge pattern of skin through direct contact. A millimetre of TPU between finger and sensor does not weaken the signal — it blocks it. No material solves this.
What this means in practice
If Apple's foldable ships with side-button Touch ID, every rugged case using a covered power button will break the unlock. Not degrade it. Break it.
Three ways button cutouts go wrong
1. Too small
Your finger needs enough contact area for a reliable read. If the case wall crowds the button you get partial contact and intermittent failures — works four times in five, and you cannot work out why. Foldable case walls are often thicker than slab-phone walls, which makes this worse.
2. Too large
Oversize it and you lose rigidity exactly where the phone needs it. The power-button rail absorbs a lot of drop energy, and on a folding phone the frame is already carrying more stress than a sealed slab.
3. The case sits proud of the button
If the wall is thicker than the button's protrusion, your fingertip cannot make flat contact — you are pressing into a well. This is the most common failure and the least visible in product photos. A case can look perfect and still fail to unlock reliably.
Getting all three right needs the real button geometry: protrusion height, travel, exact position on the rail. None of that appears in a leaked spec sheet.
Why it matters more on a foldable
The rail is crowded. On a book-style foldable the power button, volume rocker and hinge share one narrow edge. A cutout has to be placed without weakening the section next to the hinge — which is where most foldable drops land.
You press it far more often. A foldable is opened and closed constantly, and the cover screen means you use the closed device heavily. An unlock that fails one press in five is genuinely irritating at foldable usage rates.
What Samsung already taught the industry
This is not hypothetical. The Galaxy Z Fold line has used a side-mounted fingerprint sensor for several generations — Z Fold 7, Z Fold 8 and Z Fold 8 Ultra all do.
What we have learned designing around it:
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Open cutout, always. There is no covered-button design that works with a capacitive sensor.
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Chamfer the opening. A bevelled edge lets the fingertip sit flat instead of dropping into a square well.
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Thin the wall at that point specifically, and add the material back elsewhere on the rail.
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Test with more than one finger. Thumb and index approach at different angles; a cutout that works for one can fail the other.
If Apple goes side-button Touch ID, that experience transfers directly. If Apple does something else, the analysis changes — which is exactly why we are not committing to a design before 9 September.
What to check before you buy
| Check |
Why |
| Is the power button covered or open? |
Covered means the sensor will not read. Non-negotiable |
| Is the cutout chamfered? |
A square well stops the fingertip sitting flat |
| Does the seller mention the sensor at all? |
If they have not thought about it, they have not tested it |
| Was it designed after the phone shipped? |
Button geometry is not in leaked specs |
We test this properly
Get our unlock test after launch
Once Apple confirms the biometrics, we will publish what the button geometry means for cases — and which designs actually pass an unlock test. One email.
Frequently asked questions
Will the iPhone Fold have Touch ID or Face ID?
Apple has not confirmed either. Reporting ahead of the 9 September 2026 event points to Touch ID in the side button rather than Face ID. Treat it as reported rather than certain until Apple announces.
Can a case cover a side-button fingerprint sensor?
No. Capacitive fingerprint sensors need direct skin contact. Even a thin layer of case material blocks the reading rather than weakening it, so the case must use an open cutout at that button.
Will rugged cases work with side-button Touch ID?
Only if they use an open cutout at the power button. Many rugged designs cover every button in a continuous wall of material for sealing and drop performance, and those will prevent the sensor from reading.
Does Samsung's Galaxy Z Fold have the same issue?
Yes. The Galaxy Z Fold 7, Z Fold 8 and Z Fold 8 Ultra all use a side-mounted fingerprint sensor, so foldable case makers have already had to design around this constraint.
What should I look for in the cutout itself?
A chamfered opening so the fingertip sits flat against the sensor, sized for full contact but not so large that the side rail loses rigidity. The case wall should not stand proud of the button.
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