How to stop people reading your phone screen over your shoulder
The short answer: a privacy screen protector is the only thing that physically narrows the viewing angle, a built-in privacy display does the same job better if your phone has one, and a screen shade app is the only option that is free, instant, and reversible. Seating position and smaller text help a little. Lowering brightness barely helps at all. Below is what each one actually does.
1. Change where you sit and how you hold the phone
This costs nothing and it works. Put your back to a wall or a window, sit at the end of a row rather than the middle, and tilt the phone toward your own chest instead of holding it flat. A screen tilted 30 degrees away from the person beside you is already hard to read at arm's length.
Limit: on a packed train you often cannot choose your seat, and you cannot tilt away from two people at once.
2. Shrink the text and turn down the brightness
Smaller text genuinely reduces what a neighbour can pick up, because they are reading at a longer distance than you are and small type falls apart first.
Limit: brightness is the weaker half of this pair. At night a dim screen is less noticeable, but in a lit carriage the person next to you sees the same thing you do — if you can read it, so can they. And you pay for both changes with your own eyes.
3. A privacy screen protector
This is the real fix for shoulder surfing. A privacy film has a microlouvre layer — think of very fine vertical blinds laminated into the sheet — so light leaving the screen at a wide angle is blocked. Someone more than roughly 30 degrees off centre sees a dark panel, and they see it whatever app you are in.
Limits: you lose brightness head-on, so you push the backlight higher and drain more battery. It is permanent until you peel it off, which is annoying when you want to show someone a photo or watch a video with a friend. Film quality varies, fit varies by model, and a film that covers a curved edge or a fingerprint sensor badly is worse than no film. And it costs money per device.
4. A built-in privacy display
Some recent phones can narrow their own viewing angle in software, at the panel level. This is the best version of the idea: no film, no brightness penalty when it is off, and you toggle it from the quick settings.
Limit: you need a phone that has it. No app can add this feature to a phone that does not — the hardware is doing the work. Be careful with ads that show this effect while selling you an app; an app cannot change your display's optics.
5. A screen shade app
A shade app draws a layer over whatever is on screen and hides most of it, leaving only the part you are actually reading visible. It is free, it works on the phone you already have, and you turn it on and off in a second.
Limit: be clear about what this is. Software cannot change the viewing angle of a panel — anyone who can see your screen can see whatever the shade leaves uncovered. What it reduces is how much is exposed at once: a neighbour glancing over sees a few words instead of your whole inbox, your whole chat thread, or your bank balance.
Which one to pick
If you read sensitive things on a commute every day and you do not mind the trade-offs, buy a privacy film. If your phone has a built-in privacy display, use it. If you want something today, for free, that you can switch off when you want to show a friend a video, use a shade app. They also stack — a film and a shade app solve different halves of the problem.
Peekless
Peekless is the shade-app option, built so it does not make your own phone unusable. It covers the screen and opens a small readable window where you are looking, instead of blacking everything out. You can move and resize the window, and turn the whole thing off from the notification shade. It works offline and asks only for the overlay permission it needs to draw.