Short answer: screen guards come in two materials — plastic films and tempered glass — and then in finishes laid over either. Films guard against scratches. Glass guards against scratches and takes the hit in a drop. The finish decides how the screen looks: clear, matte, private or tinted.
Films: PET, TPU and hydrogel
PET film is the thin, cheap plastic sheet. It stops light scratches and little else: it adds almost nothing in a drop, and it marks easily itself.
TPU and hydrogel are thicker, softer films. They stretch, so they can wrap a curved screen edge to edge, and light marks on them tend to fade back out. Many phone shops cut hydrogel to order on a machine. The trade-off is feel and look: they are softer under the finger than glass, can show a slight texture, and can yellow with age.
Tempered glass
A thin sheet of glass, toughened by heating and fast cooling, bonded to the screen. It is scratch-resistant to the top of the pencil-hardness scale (9H), it feels like the screen itself, and in a drop it cracks so the display underneath does not. For most phones it is the best all-round protection. Its limit is curves: rigid glass cannot follow a screen that bends at the sides, so on curved phones it has to stop just inside the bend.
UV glass
Tempered glass bonded with a liquid adhesive that is spread across the screen and cured under a UV lamp. Because the liquid fills the curve, it covers curved-edge screens fully. It takes longer and more care to fit, too much adhesive can seep to the edges, and it is harder to remove cleanly than a dry-adhesive sheet.
Ceramic and "unbreakable" guards
Flexible hybrid sheets, often sold as ceramic or unbreakable. They bend instead of shattering, which is why they survive a drop in a demonstration. The surface is softer than tempered glass, though, so it scratches and scuffs more over months of use.
Finishes: clear, matte, privacy, anti-blue
Clear keeps the screen exactly as its maker calibrated it, and is the right default for photos and video.
Matte (anti-glare) is etched or coated to scatter reflections. It is easier to read in sunlight and hides fingerprints, which suits gaming. The image looks a little softer, and some show a faint sparkle on sharp screens.
Privacy guards carry a micro-louvre layer that narrows the viewing angle, so the screen looks dark from the side beyond roughly 30 degrees. Useful on a train or in an open office; the cost is a dimmer picture head-on, around 15–20% less perceived brightness.
Anti-blue-light guards are tinted. They shift the screen's colours warmer all the time. Your phone's own night-light setting does the same job and can be switched off when you want true colour back.
Whichever type you choose, the cut matters more than the material. A guard cut for a different panel leaves gaps at the corners, and gaps are where dust gets in and lifting starts.
Which should you buy?
For a flat screen: clear tempered glass cut for your exact model, with full-surface adhesive. For a curved screen: glass cut to stop just inside the curve, UV glass, or a hydrogel film if edge-to-edge coverage matters more than feel. Add a matte or privacy finish only if glare or onlookers are a real problem for you — both cost some picture quality.
Questions people ask
Which type of screen guard is best for mobile?
For most phones, clear tempered glass cut for the exact model, with adhesive across the whole face. It resists scratches, takes the hit in a drop and feels like the original screen. Curved screens need a sheet cut inside the curve, UV glass, or a flexible film.
What is the difference between a screen guard and tempered glass?
"Screen guard" covers every type, including thin plastic films. Tempered glass is one type: a toughened glass sheet that protects against drops as well as scratches, where most films only stop scratches.
Is UV glass better than normal tempered glass?
Only on curved-edge screens, where its liquid adhesive fills the curve and covers the screen fully. On a flat screen a dry-adhesive tempered sheet is easier to fit and remove and protects just as well.
Are ceramic or unbreakable screen guards good?
They survive drops without shattering, but their surface is softer than tempered glass, so they scratch and scuff more with daily use.