Fingerprint Sensors on Budget Phones: Side-Mounted vs In-Display, and Why Face Unlock Is Not Equal
An in-display fingerprint sensor sounds like the premium option, so a budget phone that moves the reader under the screen can look like the more advanced buy. On cheap phones, that ordering is backwards more often than marketing admits. The plainer side-mounted reader — often built into the power button — is the one that tends to be fast, reliable and less troubled by moisture. Start with that reversal, then decide which placement suits your hands.
What the myth gets wrong about cheap in-display readers
On most other handsets, basic face unlock is offered alongside a fingerprint reader, and the fingerprint side deserves scrutiny of its own. Cheap under-display scanners have a small target area: place a finger slightly off the marked spot and the phone will not recognise it. They also tend to be sensitive to moisture, so a slightly wet or sweaty finger makes unlocking harder, and they are noticeably slower than more advanced under-display readers and than physical scanners.
None of that makes an in-display reader unusable. It makes it a feature to verify rather than a feature to pay extra for on a budget phone. A headline that counts the placement as an upgrade, without noting target size, moisture or speed, has told only the flattering half.
Three placements, side by side
| Placement | Where it sits | Strength on a budget phone | Watch for |
|---|---|---|---|
| Side-mounted | In the power button, as on the Samsung Galaxy A15 5G and Xiaomi Redmi Note 13 5G cited in the source used here | Physical scanners are generally fast and reliable, and much more resistant to moisture than under-display versions | A small power-button target still needs the registered finger placed on it |
| In-display | Under the screen, on a marked area | No separate button; the reader sits where a thumb already rests on the screen | Small target, moisture sensitivity and slower recognition on cheap versions; screen protectors can interfere, as the next section covers |
| Face unlock (basic, camera-based) | The front camera | No touch needed to open the phone | Does not usually work in the dark and can sometimes be fooled with a picture; it is not a substitute for a fingerprint reader |
The side-mounted design does not sacrifice a modern look to do its job. Building the sensor into the power button keeps the reader where a hand already goes to wake the phone. For a budget buyer, that ordinary placement is often the practical advantage, not a missing feature.
Face unlock is not the fingerprint reader's equal
This distinction matters for money as well as for opening the phone. Samsung has restated that facial recognition on Galaxy phones can only be used for opening the device and cannot be used to authenticate access to features requiring stronger security, such as Samsung Wallet, while the fingerprint reader offers the highest level of security among the lock types it describes.
So treat the two as different tools. Face unlock is a convenience for getting to the home screen when it works. A fingerprint reader is the biometric to enrol for the phone's stronger authentication tasks. A budget phone that advertises face unlock prominently and a fingerprint reader quietly has its priorities arranged for the brochure, not for the buyer.
Either biometric still sits on top of a backup. Setting up fingerprint unlock requires a backup PIN, pattern or password first, and that backup is what the phone falls back on when a fingerprint is not recognised or after a restart. Choose a backup you can remember under pressure; the fastest reader on the shelf does not remove that step.
The screen protector check nobody mentions at the till
A protector fitted after enrolment can change how an in-display reader behaves. Google's guidance for Pixel phones says a screen protector that is not Made for Google-certified may interfere with the function or security of the fingerprint sensor, and advises re-enrolling a fingerprint if one was added before a protector was put on, or after a protector was recently updated. Samsung gives the matching warning in its own guidance: pre-installed plastic protectors are designed to work with in-display sensors, and third-party protectors may affect recognition.
A side-mounted reader in a power button is not read through the screen at all, which is one reason the protector question belongs mainly to in-display models. If you choose in-display, budget the minutes to re-enrol after fitting a protector — and do it at home, not when a failed unlock is blocking something urgent.
Set up a fingerprint properly: the documented procedure
The exact menu names differ by maker, and both paths below are the makers' own. On Pixel, Google's path is Settings, then Security and privacy, then Device unlock, then Fingerprint and Face Unlock, then Fingerprint Unlock. On Samsung Galaxy, the path is Settings, then Security and Privacy, then Biometrics, then Fingerprints. For a side-mounted Samsung reader, press the power button while placing a finger on the sensor.
- Set the backup first. Add the PIN, pattern or password the phone asks for before fingerprint enrolment.
- Follow the on-screen enrolment fully. On Pixel, touch and hold as the fingerprint icon moves, changing the finger's position slightly each time and placing the sides of the finger on the sensor when prompted.
- Cover the whole finger. Samsung's guidance stresses ensuring a finger fully covers the sensor during registration.
- Mind dry fingers. Google's tip for excessively dry fingers is to moisturise before scanning, for best results.
- Re-enrol after a protector change on an in-display model, following the guidance in the previous section, then test the unlock several times.
What success looks like: the registered finger unlocks the phone repeatedly from the grip you normally use, the backup PIN still works when you deliberately choose it, and — on an in-display model — the same test passes after any screen protector is fitted.
Which placement fits you
A short decision list
- Hands are often wet, sweaty or outdoors: favour a side-mounted physical reader, for its greater moisture resistance over cheap under-display versions.
- You like the in-display position: accept a smaller target and slower recognition on a cheap version, fit a compatible protector, and re-enrol afterwards.
- You planned to rely on face unlock alone: reconsider. On basic systems it may fail in the dark, and it cannot replace the fingerprint reader for stronger authentication such as a wallet.
- Several grips, several fingers: enrol the fingers you actually unlock with, in the positions the enrolment prompts ask for, instead of registering one perfect pose you never repeat.
A fingerprint reader is used more often than almost any other part of a phone. Under $300, the sensible order is reliability first, placement fashion second: a side-mounted reader that opens the phone first time, in ordinary conditions, is worth more than an under-display reader that only looks like the future.
Our take: Do not pay a budget premium for in-display placement alone. Cheap under-display readers bring a small target, moisture sensitivity and slower recognition; a side-mounted reader in the power button is generally fast and reliable, and face unlock — convenient as it is — is for opening the phone, not for the authentication jobs a fingerprint reader handles.
— Dex Carter, Tech Writer