Visual Design
Stroke Weight
Stroke weight is how thick the lines of an icon or letterform are. It is measured by the width of the stroke, much like the nib of a pen.
Why it matters
Stroke weight sets the tone of an interface, from delicate and light to bold and grounded. Getting it wrong makes icons either disappear or feel clumsy.
In depth
Stroke weight should scale with size rather than staying fixed: thin strokes vanish when small and look frail when blown up large. Many icon sets ship in multiple weights for exactly this reason, letting you match the line to the context. A common mistake is reusing one weight everywhere and wondering why icons feel inconsistent next to the text around them.
Real-world example
A hairline-thin search icon looks elegant in a large header but vanishes when shrunk to a small toolbar size. The same icon needs a heavier stroke to stay legible at small sizes.
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