Check Web Font Delivery with an Origin Header, Too: How a Fallback Font Went Unnoticed on My Site for 13 Days
For 13 days, the Latin web font on my own site kept returning 404 and every page was drawn in a fallback face. A plain curl returned 200; only the browser's request, which carries an Origin header, received the stale 404. Here is a script that compares three kinds of request, a setting that keeps long cache lifetimes off error responses, and how to pick a purge that reaches every variant.
Dropping a Japanese Web Font Cut FCP from 4.1s to 1.7s; Half My Explanation Failed a Minimal Repro
Mobile FCP on PageSpeed fell from 4.1s to 1.7s once I stopped serving a Japanese web font. Self-hosting made it worse, and the render-blocking story did not reproduce.
I Edited a Sentence and Only the New Characters Turned into Tofu: Adding a Missing-Glyph Check to a Subsetted Japanese Web Font
Change one line of Japanese copy and the newly added characters can render as tofu boxes. Here is a small script that lists every character missing from a subsetted font, with file and line number, and fails the build if even one is absent, with real output from running it.