Readability first.
HOW MANY
Two. One for headings, one for body text. Or one used at different weights.
More than two looks disorganised and slows the page, since each font is a download.
WHAT MATTERS
Readability at small sizes on a phone Sufficient weight difference between headings and body Enough character shapes to be distinguishable
WHAT TO AVOID
Decorative fonts for body text Very light weights, which are hard to read Fonts chosen because they look unusual
SIZE
Body text at sixteen pixels or larger. Anything smaller is difficult on a phone.
Headings clearly larger than body text, with a visible step between levels.
LINE LENGTH AND SPACING
Lines that run the full width of a wide screen are hard to read. Constrain text to a comfortable measure.
Give lines room to breathe.
PERFORMANCE
Each font weight is a separate download. Load only the weights you use.
System fonts load instantly and look perfectly professional.
THE TEST
Read a paragraph on your phone. If it is effortful, the font, size or contrast is wrong.
