What is glyphhanger?

Glyphhanger is a tool that helps websites load faster by shrinking font files down to only the characters a site actually uses. Most web fonts ship with hundreds or even thousands of glyphs covering every possible character in a language. But if your site only uses basic English letters and a handful of punctuation marks, you are forcing visitors to download a lot of unnecessary data. This utility trims the fat, so to speak, keeping only what you need. At a high level, the tool works by looking at your website's actual text content and figuring out exactly which characters appear. Then it subsets your font files, meaning it creates a new, smaller version of those files containing only that specific set of characters. It also automatically determines the right unicode-range values, which are bits of code that tell the browser which font file to use for which characters. This is especially handy if you want to serve a tiny font for most of your text but still keep the full font around for rare characters. This is useful for web developers, site owners, or anyone responsible for a website's performance. For example, if you run a blog with a stylish custom font, you could use this to cut your font file sizes dramatically, making pages load faster for mobile users on slow connections. It is also helpful if you use a font with extensive language support but only need a small slice of it. Instead of manually picking characters or writing configuration files, you point the tool at your site and let it figure out the trimming automatically. The project is built in JavaScript and is described as a "utility belt" for web fonts. Beyond subsetting, it can also convert fonts between formats, which helps with cross-browser compatibility. The README does not go into deeper detail on the exact workflow, but the core promise is straightforward: smaller fonts and faster websites with minimal manual effort.