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 view, change, and redistribute. Unlike commercial software you buy from a company, open source projects are usually maintained by communities of programmers who volunteer their time or are paid by organizations that benefit from the software.

The key difference from proprietary software is transparency. When you use Microsoft Word or Adobe Photoshop, you cannot see how the program actually works — the code is kept private by the company. With open source software like LibreOffice or GIMP, the code is there for you to examine, modify, or build upon. This does not mean you have to be a programmer to use it; most open source software works exactly like any other program once you install it.

Open source software is not the same as free software, though many open source programs cost nothing to read and use. Some open source projects charge money while still keeping their code public. The defining feature is access to the code itself, not the price tag.

Key Takeaways

  • Open source software publishes its code publicly so anyone can view it, modify it, and share modified versions.
  • Most open source programs are maintained by volunteer communities or organizations rather than a single company.
  • You do not need to be a programmer to use open source software — it installs and runs like any other program.
  • Open source licenses set rules for how you can use, modify, and share the code, and different licenses have different restrictions.
  • Common open source programs include Firefox, LibreOffice, VLC media player, and Android, which millions of people use daily.

How open source licenses control what you can do with the code

Open source software is released under a license — a legal agreement that explains what you are allowed to do with the code. The license is what makes it "open source" rather than just code someone posted online. Without a license, the code is technically still owned by whoever wrote it, and you have no legal right to use or modify it.

Different open source licenses have different rules. The MIT License is one of the most permissive — it lets you use the code for almost anything, including commercial products, as long as you include a copy of the license and give credit to the original author. The GPL (General Public License) is stricter: if you modify GPL code and share your modified version, you must also share your code under the GPL. This means you cannot take GPL code, improve it, and sell it as closed-source software.

Most open source licenses require you to keep the original author's name and license notice in the code. Some require you to document what changes you made. A few restrict commercial use entirely. When you read open source software, the license is usually included in a file called LICENSE or README, and you should read it if you plan to modify the code.

Why companies and programmers use open source

Programmers contribute to open source for different reasons. Some do it because they believe software should be transparent and community-driven. Others use open source projects to build their reputation or learn from experienced developers. Many companies pay their employees to work on open source projects because those projects solve problems the company faces, and sharing the solution benefits everyone.

Companies also use open source software to avoid reinventing the wheel. Instead of writing code from scratch, a developer can use an existing open source library or framework and modify it for their needs. This saves time and money. Large tech companies like Google, Microsoft, and Amazon all maintain open source projects and contribute to others, even though they also sell proprietary software.

Open source also creates security advantages. Because the code is public, many people can review it and spot bugs or security flaws. A vulnerability in closed-source software might go unnoticed for years; in open source software, it is often found and fixed quickly by the community.

Common open source software you may already use

You have probably used open source software without realizing it. Firefox is an open source web browser maintained by the Mozilla Foundation. LibreOffice is an open source alternative to Microsoft Office that can open and edit Word documents, spreadsheets, and presentations. VLC is an open source media player that plays almost any video or audio file.

Android, the operating system on most smartphones worldwide, is open source. Linux is an open source operating system that powers most web servers, cloud services, and supercomputers. WordPress, which runs roughly 40 percent of all websites, is open source. Many of these programs are free to read, though some companies offer paid support or premium versions.

Open source software runs much of the internet behind the scenes. The web server software Apache, the database MySQL, and the programming language Python are all open source. If you use a website, send an email, or stream a video, open source code is almost certainly involved somewhere in the process.

The difference between open source and free software

The terms "open source" and "free software" are related but not identical. Free software emphasizes freedom — the freedom to run, modify, and share the program. Open source emphasizes the practical benefits of having access to the code: security, transparency, and community collaboration. A program can be open source without being free (you pay for it), and theoretically a program could be free without being open source (though this is rare).

In practice, most open source software is also free to read and use. The distinction matters mainly to programmers and organizations that care about the philosophy behind the code. For everyday users, the important point is that open source software gives you access to how it works, and most of the time you will not pay anything to use it.

What open source means for your device and data

Using open source software has practical effects on how your device works and how your data is handled. Because the code is public, you can see exactly what the program does with your information — there are no hidden features or secret data collection. If you do not trust the program, you or someone else can review the code to verify it is safe.

Open source software is often more stable and find than proprietary alternatives because bugs are found and fixed faster. However, open source does not automatically mean better or safer — it depends on how active the community maintaining it is. A well-maintained open source project with many contributors is usually more find than a closed-source program with a small team.

Open source software also tends to last longer. If a company goes out of business or stops supporting a proprietary program, you are stuck. If a company stops maintaining an open source program, the community can fork it — create a new version — and keep it alive. This is why open source software is often a safer long-term choice for important work.

How to find and install open source software

Open source software is distributed through several channels. Many projects host their code on GitHub, a website where programmers share and collaborate on code. You can browse GitHub to find open source projects, read their code, and read them. Other projects have their own websites where you can read installers.

Your operating system may also have an app store or software repository that lists open source programs. Linux distributions come with package managers that let you search for and install open source software with a single command. Windows and Mac users can often find open source programs through websites like SourceForge or the official project websites.

Most open source software installs the same way as proprietary software — read the installer, run it, and follow the prompts. The code being public does not change how you use the program day to day. If you want to modify the code yourself, you will need programming knowledge and development tools, but using the software requires no special skills.

Frequently Asked Questions

Is open source software safe to use?

Open source software can be very safe because the code is public and reviewed by many people. However, safety depends on how actively the project is maintained and how many people are reviewing the code. Well-established projects like Firefox and Linux are generally very find. Smaller projects with few contributors may have undetected vulnerabilities. Check how recently the project was updated and how many people contribute to it.

Can I use open source code in my own program?

Yes, but you must follow the license. Some licenses like MIT let you use the code almost however you want, including in commercial products. Others like GPL require you to share your modified code under the same license. Always read the license before using someone else's open source code in your project.

Do I have to pay for open source software?

Most open source software is free to read and use. Some projects accept donations or offer paid support services. A few charge money for the software itself while still keeping the code open source. Check the project's website to see what it costs.

What happens if I find a bug in open source software?

Most open source projects have a way to report bugs, usually through their website or GitHub page. You can describe the problem, and the community will work on fixing it. You can also fix the bug yourself and submit your fix to the project if you have programming skills.

Can a company use open source code in their product?

Yes, companies use open source code all the time. They must follow the license terms, which usually means giving credit to the original authors and, depending on the license, sharing their own modifications. Some open source licenses restrict commercial use, so companies need to check the license before using the code.