MIT License facts for kids

Quick facts for kids
MIT License

Copyright	Massachusetts Institute of Technology
DFSG compatible	Yes
Free software	Yes
OSI approved	Yes
GPL compatible	Yes
Copyleft	No
Linking from code with a different license	Yes
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The MIT License is a special set of rules for computer programs, like a permission slip. It came from the Massachusetts Institute of Technology (MIT) a long time ago. This license is very "permissive," meaning it lets people do a lot with the software. It's also very "compatible," so it works well with many other software rules.

Unlike some other licenses that make you share your changes (called copyleft licenses), the MIT License lets you use the software in your own private programs. You just have to include a copy of the MIT License rules and the original copyright notice with your software. In 2015 and 2025, the MIT License was the most popular software license on GitHub, a huge website where people share code.

Many famous projects use the MIT License. These include the X Window System (which helps computers show graphics), Ruby on Rails (for building websites), Node.js (for running JavaScript code), Lua (a programming language), jQuery (for making websites interactive), .NET (a software framework), Angular, and React (both for building web interfaces).

What the License Says

The MIT License has a special code: MIT. It's also sometimes called the "Expat License". It has simple rules that allow people to use, copy, change, and share the software.

Here's what the main parts of the license mean:

• Permission Granted: Anyone who gets a copy of the software can use it for free. They can also copy it, change it, combine it with other software, publish it, give it away, or even sell it.
• Conditions: You must always include the original copyright notice and the license rules with any copies of the software you share.
• No Warranty: The software is provided "as is." This means the original creators don't promise it will work perfectly or that it's good for any specific purpose.
• No Liability: The original creators are not responsible if something goes wrong or if you have problems using the software.

Different Versions of the MIT License

X11 License

The X11 License is a slightly different version of the MIT License. It was used by the X Consortium. Its special code is X11.

The main difference is that this version adds one extra rule: you cannot use the name of the original creators to advertise or promote your software without their permission.

MIT No Attribution License

The MIT No Attribution License is another version, with the code MIT-0. It was officially approved in August 2020. This version is very similar to putting software into the "public domain." This means it's almost like anyone can do anything with it, without even needing to include the copyright notice.

The main idea is that you can use, copy, change, and share the software without any restrictions. Just like the regular MIT License, it also says that the software is provided "as is" and the creators are not responsible for any problems.

Other Variations

There are a few other versions of the MIT License. For example, MIT-advertising is a version that has an extra rule about advertising.

There's also something called the Anti-Capitalist Software License (ACSL). It's based on the MIT license but adds rules about who can use the software. It's not considered a "free software" license because it limits use to certain types of organizations, like non-profits.

Why the Name "MIT License" Can Be Confusing

The name "MIT License" can sometimes be a bit confusing. That's because the Massachusetts Institute of Technology has used many different licenses over the years. For example, they use different licenses for different software projects.

Sometimes, "MIT License" refers to the Expat License (used for a program called Expat). Other times, it refers to the X11 License (used for the X Window System). Even the Open Source Initiative, which approves open-source licenses, uses "MIT License" to mean the same thing as the Expat License. Because of this, some people prefer to use more specific names to avoid confusion.

The Free Software Foundation even suggests not using the general term "MIT License" because it can be misleading.

The X Window System, which is now managed by the X.Org Foundation, uses a version of the MIT License. This version adds a small phrase to make it clear that the part about not being responsible for problems must also be included when you share the software.

Websites like GitHub, where many developers share their code, usually just call the Expat version the "MIT License." They don't usually show the small differences between the versions.

How It Compares to Other Licenses

BSD Licenses

The original BSD licenses had a rule that said you had to mention the original creators in any advertising for the software. This "advertising clause" is no longer used by the University of California, Berkeley, but it was in a modified MIT License used by XFree86.

The University of Illinois/NCSA Open Source License mixes parts of both the MIT and BSD licenses. Its rules about what you can do with the software and the "no warranty" part come from the MIT License.

The ISC license is also similar to the MIT and simpler BSD licenses. The main difference is that it removes some legal language that isn't really needed anymore.

GNU General Public License

The GNU General Public License (GPL) is different from the MIT License. The GPL is very clear about what happens with patent rights when you share software. The MIT License doesn't talk about patents at all. Also, the GPL affects any new software you create based on the original (called "derivative works"), but the MIT License does not.

Patents and the MIT License

The MIT License, like the BSD license, doesn't directly talk about patents. These licenses were created before software patents were common in the US. Other licenses, like the Apache License version 2.0, are similar but they do include clear rules about patents.

In the US, the MIT license uses words like "sell" and "use." These words are also used in US patent law. Some experts think this means the MIT license might indirectly give permission to use any patents related to the software, even if it doesn't say so directly.

Where It Came From

One of the people who helped create the MIT license, a computer scientist named Jerry Saltzer, has shared his memories and old documents about how it started.

How Popular Is It Now?

According to GitHub’s Innovation Graph from 2025, about one-third of all projects on their platform that state a license use the MIT License. This makes it the most popular license they track. Also, the Open Source Initiative reported that its MIT License page received over a million unique visitors in 2024. This was more than four times the traffic of the next most-viewed license, showing how important the MIT License remains to software developers.

See also

In Spanish: Licencia MIT para niños

• Comparison of free and open-source software licenses
• ISC license—similar to the MIT license, but with language deemed unnecessary removed
• Category:Software using the MIT license