Target Size (Minimum)
The size of the target for pointer inputs is at least 24 by 24 CSS pixels, except when there is equivalent spacing, the target is inline, its size is determined by the user agent, or a particular presentation is essential.
In plain language
Clickable things (buttons, links, icons) need to be big enough to tap or click accurately — at least about 24x24 pixels, or have enough space around them if they're smaller.
Why it matters
People with motor disabilities, hand tremors, or who are simply using a phone on a bumpy bus, can easily miss a tiny target and tap the wrong thing next to it. Small, cramped controls make the site frustrating or unusable.
In practice
Fails this criterion
A row of six small icon buttons, each only 20x20 pixels, are placed right next to each other with no gap, making it easy to tap the wrong one.
Meets this criterion
The same row of buttons is spaced out enough that even though each icon is small, there's no risk of accidentally tapping the neighboring one.
Test it yourself
Try tapping or clicking small buttons and icons on the site, especially rows of them close together. Do you frequently miss and hit the wrong one? If controls are small and cramped together, this criterion is failing.