Open source software is code that anyone can read, modify, and share

Open source software is a program where the underlying code — the instructions that make it work — is publicly available for anyone to see, change, and redistribute. This is different from closed-source software, where the company keeps the code secret and you can only use the program as they built it. With open source, you get transparency: you can look at exactly what the software does, spot problems yourself, or hire someone to fix them.

The key difference is legal permission, not just visibility. Open source software comes with a license that explicitly allows you to view the code, modify it for your own use, and share your changes with others. Some licenses require you to share improvements back with the community; others let you keep changes private. Either way, the original software remains free to use.

Key Takeaways

  • Open source code is publicly readable and modifiable, while closed-source code is kept secret by the company that owns it.
  • Open source software comes with a legal license that permits viewing, changing, and sharing the code — the license type determines what you can do with modifications.
  • Common open source programs include Firefox, LibreOffice, VLC media player, and WordPress, all of which you can use without paying.
  • You do not need to be a programmer to benefit from open source software; most users simply download and run it like any other program.
  • Open source projects are often maintained by communities of volunteers, though some large projects have corporate backing.

How open source licenses work

An open source license is a legal document that comes with the software and tells you what you can and cannot do with it. The license grants you the right to use the code, study it, modify it, and distribute it — but the exact rules depend on which license the project chose. Some of the most common are the MIT License, the GNU General Public License (GPL), and the Apache License.

The GPL is the strictest: if you modify the software and share it with others, you must share your changes under the same GPL license. This keeps the code open throughout the chain. The MIT License is more permissive — you can modify the code and keep your changes private, or sell a product built on top of it. The Apache License sits in the middle and includes patent protections. None of these licenses cost money; they simply define what you are allowed to do.

For most users, the license details do not matter. You download the software, install it, and use it. The license matters if you plan to modify the code, redistribute it, or build a product on top of it. If you are just running the program, you follow the same rules as any other software: use it for its intended purpose and do not break the law with it.

Common open source software you may already use

Many programs you use every day are open source, even if you did not know it. Firefox is an open source web browser maintained by Mozilla. LibreOffice is a free office suite (word processor, spreadsheet, presentation software) that works like Microsoft Office. VLC is a media player that plays almost any video or audio file. WordPress powers roughly 40 percent of all websites on the internet.

On phones and computers, Android is open source — Google built it on top of the Linux kernel, which is also open source. Linux itself runs most of the servers that power the internet, including the ones that host your email and the websites you visit. Blender is a free 3D modeling and animation tool used by professionals. Audacity is a free audio editor. All of these are completely free to download and use, and all of them are maintained by communities or organizations that believe in keeping the code open.

Why companies and individuals choose open source

Developers choose open source for different reasons. Some believe software should be free and transparent — that users deserve to know what code is running on their devices. Others find that open source development moves faster because many people can spot bugs and contribute fixes. A programmer in Japan can submit an improvement, a programmer in Brazil can review it, and the whole community benefits.

Companies use open source for practical reasons too. Building on top of existing open source code saves time and money. A startup can use Linux, Apache, and other open source tools to launch a service without paying licensing fees. Some companies contribute to open source projects because they use them internally and want to make sure the software stays reliable and secure. Red Hat, Canonical, and Mozilla are companies built partly on supporting and developing open source software.

Security is another reason. When code is public, more people can review it and spot vulnerabilities. A closed-source program might have a security flaw that nobody outside the company knows about for years. An open source program with thousands of eyes on it is more likely to have problems found and fixed quickly.

The difference between free software and open source

These terms are related but not identical. Free software is a philosophy: the belief that users should have the freedom to run, study, modify, and share software. Open source is a practical approach: making the code public so people can review it and improve it. Most free software is also open source, but not all open source software is free — some open source projects charge money for support or commercial versions.

The Free Software Foundation, founded by Richard Stallman, emphasizes user freedom. The Open Source Initiative, founded later, emphasizes practical benefits like security and faster development. Both groups support the same licenses and the same code, but they frame the argument differently. For your purposes as a user, the distinction rarely matters. If a program is open source, you can see the code and usually run it without paying.

How to find and use open source software

Finding open source software is straightforward. GitHub is the largest repository of open source code in the world — you can search for any type of program and find dozens of options. SourceForge and GitLab are other large repositories. Many projects also have their own websites where you can download the latest version directly.

Installation works the same way as any other software. You download the installer or the program file, run it, and follow the prompts. Some open source software requires you to compile the code yourself (convert it from human-readable instructions into machine-readable instructions), but most projects provide pre-built installers for Windows, Mac, and Linux so you do not have to. If you are not a programmer, look for a download link labeled "Release" or "Stable" — that is the version ready for regular users.

Support varies by project. Large projects like Firefox and LibreOffice have documentation, forums, and active communities. Smaller projects might have less support, but the code is still available for anyone to read and improve. If you find a bug, you can report it on the project's issue tracker, and volunteers or maintainers may fix it.

Open source versus proprietary software: what you should know

Proprietary software is owned by a company that keeps the code secret. Microsoft Office, Adobe Creative Suite, and macOS are proprietary. You pay for a license to use them, but you cannot see or modify the code. The company decides when to release updates, what features to add, and when to stop supporting old versions.

Open source software gives you more control. If a project stops being maintained, you or someone else can fork it (create a copy and continue development). If you need a feature that does not exist, you can add it yourself or hire a developer to add it. If the software has a security problem, you do not have to wait for the company to fix it — you can fix it immediately or switch to a version that has been patched.

The trade-off is that open source software sometimes has less polish or fewer features than proprietary alternatives. A commercial software company has a budget to hire designers and developers full-time. An open source project relies on volunteers, though some large projects have corporate backing. In practice, many open source programs are as polished and feature-rich as their proprietary competitors — Firefox competes with Chrome, LibreOffice competes with Microsoft Office, and Blender competes with expensive 3D software.

Frequently Asked Questions

Does open source software cost money?

The software itself is free to download and use. Some projects offer paid support, training, or commercial versions with extra features, but the core program is always free. You will never be charged a licensing fee to run open source software.

Is open source software safe to use?

Open source software is generally as safe as proprietary software, and sometimes safer because the code is public and many people review it. However, safety depends on the specific project. Large, well-maintained projects like Firefox and Linux are very secure. Smaller projects might have fewer people reviewing the code. Always download from the official project website or a trusted repository like GitHub.

Can I use open source software for my business?

Yes, most open source licenses allow business use. Some licenses require you to share any modifications you make, while others let you keep changes private. Check the specific license before you build a product on top of open source code, but in general, commercial use is permitted.

What if I find a bug in open source software?

Report it on the project's issue tracker, usually found on GitHub or the project website. Describe what you were doing when the bug happened and what you expected to happen instead. The maintainers or community members will review your report and may fix it. You can also fix it yourself and submit a pull request if you know how to code.

Do I need to be a programmer to use open source software?

No. Most open source software works exactly like proprietary software — you download it, install it, and use it. You only need to understand code if you want to modify the software or contribute to the project. Regular users never touch the code.