Short answer: buy the privacy screen protector that is cut for your exact phone model, narrows the view to about 30° either side, and says honestly what it costs in brightness. Then decide whether you need privacy at all — if you mostly use your phone at home, regular tempered glass looks better and costs less.
How a privacy screen protector works
A privacy screen protector is tempered glass with a filter of microscopic vertical slats — louvres — under its surface. Looking straight at the phone, you see down the gaps between the slats. From the side, the slats block the view, and past a certain angle the screen looks like a dark rectangle.
Everything that separates one privacy protector from another comes back to those slats: how steep the cut-off angle is, which directions they block, and how much light they cost.
The angle: 28°, 30°, 45°
The number on the box is the angle either side of centre at which the screen goes dark. A smaller number means a narrower view: more private, but you have to hold the phone more squarely, and it looks dimmer. A larger number is easier to live with and brighter, but the person in the next seat sees more.
Around 30° is where most people land. It is roughly the difference between your seat and the one beside it — enough to stop the passenger or colleague next to you, without making the screen fussy to read. Ours is cut at about ±30° for that reason.
What "180°" and "360°" mean on a listing
These are marketing words for which directions the filter blocks, not angles you can measure. Listings usually use "180°" or "two-way" for a filter that blocks left and right — the people beside you when you hold the phone upright. "360°" or "four-way" adds top and bottom, which also covers the phone held sideways.
Four-way sounds strictly better, but blocking more directions blocks more light. Two-way is the common choice because most prying happens from the side of a phone held upright. It is what we make, and the practical consequence is that in landscape — watching a video, say — the privacy effect changes.
What it costs you: brightness
Light the slats stop from reaching your neighbour does not reach you either. Looking straight on, a privacy protector takes roughly 15–20% off how bright the screen seems. Indoors most people raise brightness a notch and stop noticing. In direct sun it matters more, and running brighter uses more battery.
There is no privacy filter that narrows the view without taking some brightness with it. A listing promising privacy with no brightness cost is either not a louvre filter or not doing much.
Privacy vs regular tempered glass for office use
Both are tempered glass, so protection against scratches and drops is the same kind: the protector cracks so your screen does not. The difference is only what other people can see, and what that costs you in brightness.
Privacy glass is worth it if you read messages, banking apps or work chats where people pass behind or sit beside you — an open office, a shared desk, a daily commute. It is not worth it if your phone mostly lives at home or in the car: you would be paying, in brightness, for an angle nobody is looking from.
What it will not do
It does not stop someone directly behind you, looking at the same angle you are. It does not stop a camera pointed over your shoulder. It can show dark bands or a tint through polarised sunglasses. It is a filter for side angles, not a curtain — treat it as removing the casual audience, not as making the screen secret.
Questions people ask
What is the best privacy screen protector for my phone?
One cut for your exact model, with a privacy angle around 30° either side, from a seller that states the brightness cost. Fit matters as much as the filter: a privacy sheet that is slightly too small leaves a clear band at the edge that defeats the point.
Does a privacy screen protector reduce brightness?
Yes. Looking straight on, expect roughly 15–20% less perceived brightness, because the filter that blocks side angles also blocks some light coming to you. Indoors, raising brightness a notch makes up for it.
Is a privacy screen protector better than regular tempered glass?
Not better — different. Both protect against scratches and drops. Privacy glass adds side-angle privacy and costs some brightness; regular glass keeps the display exactly as it was made. Choose privacy only if people regularly sit or stand beside you while you use the phone.
What does 180-degree privacy mean?
On most listings it means two-way privacy: the screen darkens to the left and right when the phone is upright. It describes directions, not a measured angle. "360-degree" or four-way privacy also darkens top and bottom.
Does a privacy screen protector work in landscape mode?
A two-way filter is designed for the phone held upright. Turned sideways, the directions it blocks rotate with it, so the effect is different. A four-way filter covers both orientations, at a further cost in brightness.
Can the person behind me still see my screen?
Often, yes. Privacy glass blocks side angles. Someone directly behind you sees the screen from nearly the same angle you do, so the filter does little against them.