OFL (SIL Open Font License)

The SIL Open Font License (OFL) is the de facto standard for open-source fonts, created by SIL International in 2005. If you've ever used a font from Google Fonts, there's a strong chance it's distributed under the OFL — fonts like Inter, Roboto, and Lato all use it.

Understanding the OFL matters when you're building commercial products, redistributing fonts, or embedding type in downloadable assets.

What the OFL allows:

• Free use in personal and commercial projects, including websites and applications
• Modification and redistribution of the font files themselves
• Bundling fonts with software, including proprietary software

The key restriction — the Reserved Font Name clause:

If a font declares Reserved Font Names (listed in the license header), you cannot redistribute modified versions under those same names. You must rename the font if you modify and redistribute it. This protects the original font's identity while still allowing derivatives to exist.

What the OFL prohibits:

• Selling the font files themselves as a standalone product
• Removing or replacing the copyright notice and license text

For web developers, the OFL is almost entirely permissive in practice. Serving an OFL font via a CDN, self-hosting it, using it in a SaaS product — all of this is permitted. The restrictions primarily apply to type foundries or developers who want to resell modified font files commercially.

When evaluating a font for a client project, checking the license should be your first step. You'll typically find it in a LICENSE or OFL.txt file inside the font download package, or in the metadata on sites like Google Fonts or FontSquirrel. The license version (currently 1.1) also matters, as it clarified several ambiguities from the original 1.0 release.

The OFL has been remarkably successful at growing the open-source type ecosystem. It strikes the balance that made open-source software licenses successful: permissive enough for broad adoption, protective enough to give type designers confidence their work won't be commercially exploited without permission. For designers and developers working with web typography, the OFL is the license you'll encounter most often and the one that causes the fewest legal headaches.

If you're building a font tool, type specimen site, or embedding fonts in an Electron app, the OFL covers you. When in doubt, reading the two-page license directly takes less than five minutes — it's written in unusually clear language for a legal document.