Open-Source Fonts and the SIL Open Font License, Explained

Free fonts can be a wonderful resource for designers, especially when budgets are tight. But "free" can mean many different things. Some fonts are free for personal use only, others can be used commercially, and some come with conditions about modification and sharing. One of the most widely used licenses for open-source fonts is the SIL Open Font License, often abbreviated as OFL. Understanding what it allows helps you use these fonts with confidence.

Why licenses matter even for free fonts

A font is software and a creative work, and both are protected by copyright. The license tells you what you may do with it. Downloading a font without checking the terms can lead to accidental misuse, especially in client projects or products. For a broader view of the topic, our article on what "free" really means in design resources is a helpful companion.

What is the SIL Open Font License?

The SIL Open Font License is a free, open-source license designed specifically for fonts. It is used by a large number of typefaces, including many in popular open font libraries. Its purpose is to let people use, study, modify and redistribute fonts freely while protecting the integrity of the original designs.

It is not the only open license for fonts, and the exact terms of any font depend on the license file included with it. Always read the license text that comes with the specific font you are using.

What the OFL generally allows

In broad terms, the OFL permits you to:

Use the font for personal and commercial projects, including logos, print, websites and apps.
Study and modify the font, for example to adjust glyphs or add characters.
Embed the font in documents and applications, subject to the license terms.
Redistribute the font, including modified versions, provided you follow the license conditions.

Because the license is designed for the open-source community, there is generally no fee for using these fonts, and you do not need to ask for permission for ordinary design use.

What the OFL restricts

The license does include conditions, and these are important:

You may not sell the font by itself. Selling the font file as a standalone product is not allowed, although you can bundle it with other software or products under certain conditions.
Modified versions must keep the same license. If you distribute a changed version, it must also be released under the OFL.
The license and copyright notices must stay with the font when you redistribute it.
Reserved font names may apply. Some fonts reserve their names, which means that modified versions generally must be renamed.

These rules are simplified here, so read the actual text, particularly if you plan to modify or redistribute a font.

Using OFL fonts in practice

For most designers, using an open-source font in a logo, brochure, website or app is straightforward. Download the font from a reputable source, keep the license file with your project, and use it as you would any other font. Keeping that file with your project helps when someone later asks where a font came from. Habits such as these fit neatly into a tidy asset library, where you can note the source and license beside each font.

Choose trustworthy sources

Open-source fonts are available from various repositories and from the designers' own websites. Choose sources that clearly state the license and provide the full text. Be careful with sites that repackage fonts without clear licensing information, since they may host altered or mislabeled files. If the terms are unclear, look for the original designer's page.

Check for language and feature support

A license is only part of the choice. Check that the font supports the languages, accents and symbols you need, and that it includes weights and styles suitable for your design. Some free fonts include only a single style, which may limit their usefulness for complex layouts.

When to seek legal advice

For everyday design use, the OFL is usually simple. But if you plan to redistribute modified fonts, sell products that bundle fonts or work in a regulated industry, consider consulting a qualified professional. This article is general information, not legal advice.

Frequently asked questions

Can I use OFL fonts in a logo? Generally yes, since the license allows use of the font in your designs. Check the specific license file for the font you are using.

Do I need to credit the font designer? The OFL does not usually require credit for ordinary use, though acknowledging the designer is a thoughtful gesture.

Can I sell a product that uses an OFL font? Yes, in most cases, as long as you are not selling the font file by itself. Review the license for details.