Short answer: they are not alternatives. Gorilla Glass is a brand of strengthened glass that many phone makers use for the front of the phone itself. A tempered glass protector is a separate, replaceable sheet that sits on top of it. Your phone can have Gorilla Glass and still benefit from a protector, because a scratched or cracked protector costs a fraction of a new display.
What Gorilla Glass is
Corning Gorilla Glass is a trademarked family of chemically strengthened glass made by Corning, used as the cover glass on the front and sometimes the back of many phones. Other makers have their own equivalents — AGC Dragontrail, for instance, and Apple's Ceramic Shield. It is part of the phone: replacing it usually means replacing the display assembly.
What a tempered glass protector is
A protector is a thin sheet of toughened glass — ours are 0.33mm — cut to fit one phone model and stuck on with adhesive. Its job is to be the first thing a scratch or a knock meets, and to be cheap and quick to replace when it does.
Why a Gorilla Glass phone still needs a protector
Strong glass is still glass. It resists scratches from keys and coins, but sand and grit in a pocket are hard enough to scratch it, and a drop onto a hard edge can crack it. With a protector on top, the protector takes those — and you replace a sheet, not a screen.
Gorilla Glass makes the screen harder to damage. A protector makes damage cheap.
"Gorilla" on a protector listing
Some protector listings use "Gorilla" loosely to sound strong. Unless the seller says the sheet is actually made with Corning glass, treat the word as a description, not the material. Judge a protector the usual way: fit for your exact model, adhesive across the whole sheet, and an edge that suits your screen. We do not describe our glass as Gorilla Glass, because it is not.
Questions people ask
What is the difference between Gorilla Glass and tempered glass?
Gorilla Glass is Corning's brand of strengthened glass used as the phone's own front glass. A tempered glass protector is a separate, replaceable sheet stuck on top of it to take scratches and knocks.
Do I need a screen protector if my phone has Gorilla Glass?
It is still worth it. Gorilla Glass resists everyday scratches, but grit can scratch it and a hard drop can crack it — and fixing it means replacing the display. A protector takes that damage instead and costs far less to replace.
Is Gorilla Glass better than tempered glass?
They do different jobs, so one is not a substitute for the other. Gorilla Glass is the phone's built-in screen; a tempered glass protector is an extra, replaceable layer on top.
Is a "Gorilla" tempered glass protector made by Corning?
Only if the seller says so specifically. Many listings use the word to mean "strong". Look for the exact-model fit and full-surface adhesive rather than the name.