What are serifs, and do they really make text easier to read?

Serifs are the small strokes at the ends of the main strokes of a letter, the little feet and flags you see on the letters of most printed books. They began in letters carved into stone in Roman antiquity. Whether they make text easier to read is far less settled than many people believe.

Where did they come from? One explanation, proposed by Father Edward Catich in 1968 and broadly but not universally accepted, is that Roman letters were first painted onto stone, and carvers followed the brush marks, which flared at stroke ends and corners. Another theory is that serifs were devised to neaten the ends of lines as they were chiselled into stone. Handwriting rarely uses them, because they began in inscriptions.

Now the big claim: do serifs help your eye along a line of text? The evidence is mixed. Serifed typefaces are widely used for body text, and Colin Wheildon's studies found sans-serif faces impaired comprehension. But Kathleen Tinkel says studies suggest sans-serif may be only slightly less legible, and that careful setting can offset the difference. Alex Poole goes further and argues that most reasonably designed typefaces in mainstream use are equally legible.

The screen has changed the question. On lower-resolution displays, fine details like serifs may disappear or appear too large, which is why sans-serif has become the most prevalent type on computer screens. So the honest answer is that serifs are a style with a long history, not a proven reading aid.