The MIT License is one of the shortest and most permissive open-source licenses
The MIT License is a legal agreement that lets you use, modify, and share software with almost no restrictions. It was created at the Massachusetts Institute of Technology in the 1980s and has become one of the most common licenses for open-source code. If you read software with an MIT License, you can use it for any purpose — commercial or personal — change it however you want, and share your changes with others. The only real requirement is that you keep a copy of the original license and credit the original author.
The license is popular because it is short (about 170 words), clear, and gets out of your way. You are not required to share your changes back to the community, you are not required to open-source your own work if you use MIT-licensed code, and you do not have to worry about patent disputes. The tradeoff is that the original author gives no warranty — if something breaks, that is your problem to fix.
Key Takeaways
- MIT-licensed software can be used, modified, and sold for any purpose without asking permission, as long as you include the original license text and credit the author.
- You do not have to share your changes or release your own code as open-source if you use MIT-licensed software in your project.
- The license provides no warranty or may provide that the software will work correctly or safely.
- MIT is one of the most permissive licenses available, which is why it is used by major projects like Node.js, Rails, and the X Window System.
What you can do with MIT-licensed software
Under the MIT License, you have broad freedom. You can read the code and use it in your own project without asking anyone. You can modify it to fit your needs. You can sell software that includes MIT-licensed code. You can use it in a closed-source process that you do not share with anyone. You can combine it with code under other licenses (with some exceptions for licenses that conflict). None of these actions require permission or notification.
This freedom is why companies use MIT-licensed libraries in commercial products. If you are building an process and you want to use a popular library — say, a tool for parsing dates or handling web requests — and it is MIT-licensed, you can drop it in and move forward. You do not have to negotiate, wait for approval, or worry about being forced to open-source your own work.
What the MIT License requires from you
The MIT License has only two real requirements. First, you must include a copy of the license text and the copyright notice in any copy or substantial portion of the software you distribute. This means if you share your code with others — whether you sell it, give it away, or publish it — you need to include the original MIT License file and the author's name. Second, the license must state that the software is provided "as is" with no warranty.
These requirements are minimal compared to other open-source licenses. You do not have to publish your source code. You do not have to document what you changed. You do not have to notify the original author. You do not have to release your own improvements back to the community. If you use MIT-licensed code in a closed-source product and never share it with anyone, you technically do not even need to include the license — but if you do share it, you must include it then.
How MIT compares to other open-source licenses
The MIT License sits at the permissive end of the open-source spectrum. On the other end are copyleft licenses like the GPL (GNU General Public License), which require you to open-source any code you build with them and release it under the same license. In the middle are licenses like Apache 2.0, which is similar to MIT but includes explicit patent protection language.
If you are choosing between licenses for your own code, MIT is the choice when you want maximum freedom for others to use your work however they want. GPL is the choice when you want to may support that improvements stay open-source. Apache 2.0 is the choice when you want permissiveness plus legal protection against patent claims. For someone using existing code, MIT is the easiest to work with because it imposes the fewest restrictions.
Where you will encounter MIT-licensed software
MIT-licensed code is everywhere in modern software development. Node.js (the JavaScript runtime), Ruby on Rails (a web framework), jQuery (a JavaScript library), and the X Window System (the foundation of graphical interfaces on Linux) are all MIT-licensed. Many smaller libraries and tools use it as well. When you read code from GitHub or npm (the Node.js package manager), you will often see MIT in the license field.
The prevalence of MIT licensing means that if you are building software, you will almost certainly use MIT-licensed code at some point. Understanding what the license allows and requires helps you avoid legal problems and use the code confidently. Most of the time, including the license file in your project and crediting the author is all you need to do.
What MIT does not cover
The MIT License covers the code itself, not trademarks or brand names. If software is MIT-licensed, you can use and modify the code, but you cannot use the original author's name or logo to promote your version without permission. You also cannot claim that your modified version is endorsed by the original author.
The license also provides no warranty. If you use MIT-licensed code and it causes problems — it crashes, it loses data, it has a security hole — the original author is not responsible. This is why many projects that use MIT-licensed code also run their own tests and security reviews. You are responsible for verifying that the code is safe and suitable for your use.
How to include MIT-licensed code in your project
If you use MIT-licensed software, the standard practice is to copy the LICENSE file (or the license text) into your project and keep it with the code. If you are distributing your code to others, include the LICENSE file in the distribution. If you are publishing code on GitHub or another platform, the license file will usually be displayed automatically.
If you are modifying MIT-licensed code, you do not need to create a new license or change the existing one. You can add your own copyright notice alongside the original author's, but the MIT License itself stays the same. Some projects ask you to document what you changed in a CHANGELOG or README file, but this is a courtesy, not a legal requirement of the MIT License.
Frequently Asked Questions
Can I use MIT-licensed code in a commercial product?
Yes. The MIT License explicitly permits commercial use. You can sell software that includes MIT-licensed code as long as you include the original license text and credit the author. You do not need to open-source your own code or share your changes.
Do I have to share my changes if I modify MIT-licensed code?
No. Unlike copyleft licenses, MIT does not require you to share improvements. You can modify the code and keep your changes private. If you do share your modified version, you must still include the original MIT License.
What happens if MIT-licensed software breaks my process?
The license provides no warranty, so the original author is not legally responsible. You are responsible for testing the code, reporting bugs, and deciding whether to use it. Many MIT-licensed projects are actively maintained and will fix bugs if you report them, but this is not may provide by the license.
Can I change the MIT License or create my own version of it?
You should not modify the license text itself. If you are releasing your own code, you can choose to use the standard MIT License as-is. If you need different terms, you should consult a lawyer or choose a different license that better fits your needs.
Is MIT-licensed code safe to use?
MIT-licensed code can be safe or unsafe depending on the specific project. The license itself does not may provide quality or security. Before using any open-source code, check whether the project is actively maintained, has a good reputation, and has been reviewed by others in the community.