Free sans-serif fonts

Sans-serif is the largest category here and the least helpful label: it says only what a face does not have. The useful distinction is between the three traditions inside it. Grotesques — Helvetica and its descendants — are even, closed and slightly impersonal. Geometrics are built from circles and straight lines and read as modern and a little cold. Humanists take their proportions from handwriting, which makes them the easiest of the three to read at length.

For an interface, the questions are narrow and answerable. Does it have a distinguishable 1, l and I? Does it hold together at 13 pixels? Does it come in enough weights that you can build a hierarchy without faking bold? Most of the well-known open families were drawn for screens and answer all three; the ones that were not are usually obvious within a paragraph.

For body text on a page somebody reads for minutes rather than seconds, lean humanist. The variation in stroke and the more open letterforms give the eye something to hold on to, and the difference over a thousand words is real. A geometric sans set at 16 pixels for three screens of text is a decision the reader feels without being able to name.

Variable versions are worth preferring where they exist. One file carries the whole weight range, so a page loads a single font instead of four, and you can use a weight between the named ones when the layout wants it. The one thing to check is what the file defaults to, because a handful of families default to something other than regular and the difference shows up as a hairline in Word.