Open Source

Open source software is software whose source code is published and licensed so that anyone can use, study, modify and redistribute it. The exact permissions come from the software license attached to the project.

Why it matters

Open source underpins most of the web: Linux, Apache, nginx, PostgreSQL, Python and countless libraries are open source. It lowers cost, lets you audit code and avoids dependence on a single vendor. It also means you take on responsibility for choosing maintained projects and keeping them updated.

Example

A project's repository usually contains:

README.md      what it does and how to use it
LICENSE        the legal terms
CONTRIBUTING.md how to submit changes

Before using a package, check the license, how recently it was updated and how many maintainers it has.

Common misconceptions

• "Open source means free of charge." Often it is, but the term concerns freedom to use and modify the code, and companies sell support and hosted versions.
• "Open source means no rules." Licenses still impose conditions, such as keeping copyright notices or sharing changes.
• "Anyone can change the official project." Maintainers decide what is merged.

Related

• Software license
• Dependency
• Pull request
• Package manager

This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.