Shipping Korean type only to the posts that need it

This site ships IBM Plex Sans for latin text rather than falling back to whatever the operating system has. Four faces, 57 KB together. That is cheap for the same page rendering the same way everywhere.

Korean is a different matter. Carry all 11,172 precomposed syllables and one face is over 4 MB. Nobody should download that to read one post.

Cut it per post

The method is simple. After the build, read each post’s HTML, collect the Hangul codepoints that actually appear in it, and cut a subset for that post alone.

import re
chars = set(re.findall(r"[가-힣ㄱ-ㅎㅏ-ㅣ]", html))
subset(font, unicodes=chars, output=f"fonts/ko/{slug}.woff2")

A post like this one uses a few hundred characters. The subset comes out at roughly one percent of the original, and a post written in English carries no Korean face at all.

The price

Editing a post means rebuilding its font. That is the build’s job, so it costs no attention - but editing the HTML by hand without a build is no longer possible.

And a subset is valid only for its own post. Read several in a row and each one fetches a new font. Once there are dozens of posts it would be better to fetch a shared subset of the 2,350 common syllables first and fill in the rest per post. With two posts that optimisation is premature.

Choosing the face

IBM Plex Sans KR. Same family as the latin, so the voice does not split, and OFL, so self-hosting is fine. Better than adding one more typeface to the mix.