Introduction: The "Compressed Desktop" Mistake

Mobile UX is not a desktop version that has been "compressed" to fit in the palm of your hand. It is a completely different psychology of consumption. A web user and a smartphone user are often the same person, but in different cognitive states.

1. Context is Everything

A mobile user is someone walking down the street, standing in line, or distracted by notifications. Their attention is fragmented.

One action rule: Each screen should contain one main goal. If you make the user choose between five equally weighted buttons on a small screen, you lose them.
Thumb zone: Ergonomics are more important than aesthetics. Key controls should be where they can be easily reached by a finger without having to reposition the phone.

2. Speed as a UX Parameter

On mobile devices, speed is not a technical specification but the foundation of user experience.

Optimistic UI: Show the result of an action instantly, even if the server request is still processing.
Skeleton Screens: Instead of loading indicators (spinners), use gray placeholders. This creates the impression that content is already there, reducing impatience.

3. Minimum Input, Maximum Output

Typing on a phone is painful. Good mobile UX minimizes text input:
Use autocomplete and geolocation.
Offer choices instead of blank fields.
Use biometrics instead of entering passwords. On mobile devices, "less" is not minimalism; it is the only way to survive in a world of attention scarcity.