Appearance → Customize → Typography → Heading font. Five fields: face, weight, letter case, letter spacing, line height.
It applies to h1 through h6 everywhere — post and page headlines, the headings inside your content, listing titles, widget titles, the archive title.
No size field, on purpose
Each heading level is sized individually by the stylesheet, in proportion to the others. One number here would either flatten that scale or multiply it, and both are worse than the scale the theme already has.
To change the sizes, use Additional CSS:
.single-title { font-size: 2.4rem; }
.entry-title { font-size: 1.35rem; }
Face
Empty means System default. The nine web-safe stacks and your installed families are all offered; see how the font picker works.
Setting a face here also moves the menu and the site title, because both of those default to Same as headings. If you want the headings changed but not the header, set the face you want on the Navigation and Logo controls explicitly.
The classic publication pairing is a serif for headings over a sans-serif body, or the reverse. Two faces is plenty; three is a design problem.
Weight
Default (empty) leaves the stylesheet’s 600. The dropdown offers 300 Light through 800 Extra-bold.
The font needs the weight installed, or the browser will fake it. A synthesised bold is a normal weight smeared sideways, and it looks it — thick, muddy, and slightly the wrong shape. If you installed a family through the Font Library, install the weights you plan to use; if you picked a web-safe stack, stay near 400 and 700, which is all those have.
Letter case
| Default | emits nothing, inherits whatever applies |
| None — as typed | the deliberate choice to leave the text alone |
| Uppercase | all caps |
| Lowercase | all lower case |
| Capitalize | First Letter Of Each Word |
Default and None are not the same answer: Default emits nothing and could inherit an uppercase from somewhere else, None is an instruction.
Uppercase headlines need letter spacing to be readable — capitals are drawn to sit further apart than they do by default. Try 0.04em to 0.08em.
Letter spacing
A CSS length: 0.02em, -0.01em, normal. Use em so it scales with the type.
Large display type usually wants slightly negative tracking — at 40px a headline set at -0.02em looks intentional where the default looks loose. Small type and capitals want positive.
Line height
Default 1.2. Headlines are short and want to be tight; going above about 1.4 makes a two-line headline read as two headlines.