Viewport zoom
Viewport zoom on focus is iOS enlarging the page when a user focuses an input with a font-size below 16px.
Why it matters
It is the single most common mobile defect on otherwise well-built sites, and it is one CSS rule to fix.
How it is measured
Open the site on a real iPhone, tap a form field, and confirm the page does not zoom.
Checks that involve viewport zoom
Related terms
Questions
What is viewport zoom?
Viewport zoom on focus is iOS enlarging the page when a user focuses an input with a font-size below 16px.
Why does viewport zoom matter?
It is the single most common mobile defect on otherwise well-built sites, and it is one CSS rule to fix.
How is viewport zoom measured?
Open the site on a real iPhone, tap a form field, and confirm the page does not zoom.