Since the launch of Samsung’s Galaxy S10 series, the company has included an in-display fingerprint sensor that simplifies how users interact with their mobile devices through biometrics. Optical sensor technology has been around longer – the Galaxy Note 9 had a sensor built into the bottom – but with the latest generations, you can scan your fingerprint to unlock a phone by pressing your finger on the screen, not the side or back of the device. It’s practical, works quite well and is easy to install. Even if you use a screen protector, the fingerprint scanner still works, but it also depends on the type of screen protector you install and the type of fingerprint sensor your device has.
Samsung’s ultrasonic sensor is different from an optical sensor. Ultrasonic sensors have more problems with thicker materials, while optical sensors can read fingerprints through almost any transparent material. Back when the S10 series launched, there were only a handful of viable screen protectors that also worked with the fingerprint sensor. Things have improved considerably since then, with more compatible options for newer devices.
The easiest way to find a compatible protector is to look for a “fingerprint” protector for your individual model. Most fingerprint-ready options, glass or otherwise, have a thin section of material. My Galaxy S25 Ultra’s screen protector contains a small circular area for on-screen scanning. It is only visible from a side angle; in bright environments or direct sunlight, you will never notice it. However, this thin area allows the scanner to read my print.
Identify the type of fingerprint scanner your device has
Not all in-display fingerprint sensors work the same. Samsung’s high-end S series phones, like the Galaxy S26, feature ultrasonic fingerprint scanners that work by reading and transmitting a sound pulse, which is first used to map the contours, pores and ridges of the surface of your finger. When you want to enter, the system sends a pulse, which bounces back similar to echolocation, and if it recognizes your finger by matching it to the stored card, it will unlock.
Part of the reason why lower-to-mid-quality Samsung phones are inexpensive, like the cheaper Galaxy A series, is because they contain less expensive hardware, like optical fingerprint sensors versus ultrasonic sensors. The Galaxy A57 is a great example, or the Galaxy S20 FE, both of which are more affordable and feature optical scanners. Optical scanners work similarly to ultrasound, but they reflect light from your finger to map patterns, not sound, which is why most clear protectors work well. With optical scanners, the phone will also turn on when you touch the activation area.
Since ultrasound scanners use pulses of sound and not light, you will notice that devices with these types of sensors do not need to turn on to scan or function properly. A Galaxy S25 or S26 device will unlock almost immediately when you place your finger on the on-screen sensor, even when the screen is off.
Understanding Screen Protector Types
There are two types of screen protectors: tempered glass or film (plastic). Protective films are made from TPU or PET plastic and come in a range of properties from rigid to more film-like. However, they tend to come in thinner formats overall, making them excellent candidates for devices with ultrasound scanners. The screen protectors aren’t as physically strong as a tempered glass option, but pose little problem to the fingerprint scanner. Almost all plastic or film protectors are compatible with both types of scanners because light and sound can penetrate them.
Tempered glass is generally thicker, which means you’ll need to pay attention to the properties of the protector if you want to make sure it works with your device. Usually anything thicker than 0.33mm will cause interference with an ultrasound scanner. Although some have a thinner area suitable for fingerprints. Additionally, it is not always true that glass is thicker.
There are premium glass protectors that have an ultra-thin design. You simply need to consider these properties when choosing a protector for your device, also taking into account the type of sensor installed on your Samsung Galaxy. Privacy screen protectors can cause problems with both types of sensors because they block light to reduce the viewing angle and can reduce the sensitivity of ultrasonic pulses. Although it’s hit or miss with ultrasound as sometimes they work well. It’s always best to re-scan your fingerprints after applying a screen protector.
