Reading interfaces are usually designed on a desktop with a mouse, then shipped to people holding a phone in one hand. The mismatch shows immediately, and it's the reason so many otherwise decent readers are unpleasant to use.

The thumb decides the layout

Hold a phone one-handed and the thumb sweeps a rough arc across the lower portion of the screen. Everything above that arc requires either a second hand or a grip shift, and a grip shift on a couch means a dropped phone.

So the bottom third is prime real estate and the top is effectively out of reach. Most readers put their controls at the top, following desktop convention, which is why people stop using the controls and start guessing.

Phones have also grown. What was reachable on a small handset five years ago is not reachable now, and layouts designed against old assumptions age badly.

Tap zones versus gestures

Two ways to drive a reader. Tap zones divide the screen into invisible regions — tap left to go back, right to go forward, centre to show controls. Gestures use swipes and pinches.

The best readers offer both and make the tap zones discoverable once, then get out of the way. The worst rely entirely on gestures that collide with the browser's own back-swipe, so half the time you leave the page instead of turning it.

Targets have to be big enough

A finger contact area is around nine millimetres, which translates to roughly a 44 pixel minimum for anything tappable. Smaller than that and you get mis-taps, and mis-taps in a reader mean losing your place.

This is the most frequently ignored rule in interface design, and it's the easiest to check: if two controls sit closer together than a fingertip, one of them is going to be hit by accident.

Spacing matters as much as size. A 44 pixel target flush against another 44 pixel target is still a mis-tap waiting to happen, particularly near the screen edge where the thumb arrives at an angle.

Edge gestures make the corners worse still. Modern phones reserve strips at the sides and bottom for system navigation, so a control placed there is competing with the operating system and will lose about a third of the time.

What a reader should remember

Position, zoom level, and brightness, at minimum. Losing your place because you switched apps for thirty seconds is the single most annoying failure a reader can have, and it's trivial to fix.

Direction and layout preference matter too, since vertical-scroll and page-based material need different handling — the format differences covered in our piece on vertical scroll.

Brightness deserves a mention because so much of this material is dark, and dark work suffers badly on an auto-brightness screen in a lit room, as we set out in the piece on phone-first viewing.

The privacy side of interface defaults

Ergonomics and discretion overlap. Static thumbnails until a deliberate tap, muted audio, and neutral page titles are interface decisions that happen to matter a great deal on a device people hand to other people — the subject of our piece on privacy by design.

Verified age entry belongs before any of this, at the platform layer. Characters remain fictional and unmistakably adult under the standards in the control room, and connected creation stays on models.

Building a reader for the way people actually read

Test it one-handed, on a couch, at night, with a phone larger than the one you designed on. That single test surfaces nearly every problem in this list, and almost nobody performs it.

The controls belong at the bottom, the targets belong at 44 pixels or larger, the tap zones belong on by default, and the reader belongs on the position you left it at. None of that is difficult. It's just rarely checked.