In web development, every millisecond on the critical path matters. Typography is part of your visual identity, yet a single self-hosted family can add hundreds of kilobytes before the browser paints the hero line clients actually see. That cost often shows up as slower First Contentful Paint (FCP) and a worse Largest Contentful Paint (LCP) when the LCP element is a headline set in a custom face.
Font subsetting is the practical fix: ship only the characters (glyphs) each page or component needs instead of entire typefaces built for every language and symbol you will never render.
What font subsetting is
A typical desktop font file contains thousands of glyphs: Latin extended, Cyrillic, ligatures, numerals, punctuation, and symbols you may never use on a marketing site. When you @font-face that file or pull it from a CDN, the browser still has to download and parse the whole package unless you split it.
Subsetting creates a smaller font file that includes a defined subset of Unicode code points. Examples:
