Open source software: what it is and why it runs the internet

A large share of the world’s software — including much of what powers the internet — is open source: its source code is published openly, and anyone is free to use, study, modify, and share it.

How it works

With most commercial software, the underlying code is kept private. With open source, the code is public, and its license grants everyone the right to run it, inspect how it works, change it, and distribute their changes. Popular projects are maintained by communities of contributors — sometimes volunteers, sometimes engineers paid by companies — who propose improvements that maintainers review before accepting.

Why companies rely on it

It might seem surprising that businesses build on software they do not own, but the advantages are practical. Open source is free to adopt, avoids lock-in to a single vendor, and can be inspected for security and reliability rather than taken on trust. Because many organizations use the same widely adopted projects, bugs are found and fixed quickly, and improvements benefit everyone. Operating systems, web servers, databases, and programming tools that run critical systems are frequently open source.

The sustainability question

Openness creates a challenge: who pays to maintain software that everyone uses for free? Some projects are backed by companies that depend on them; others rely on foundations, sponsorships, or grants. When a widely used but under-resourced project has a security flaw, it can affect countless systems at once — which has pushed the industry to invest more in supporting the maintainers behind key technology.

Why it matters

Open source shifted software from something you simply buy to something communities build together. It lowered the barrier to creating powerful tools, and it means the infrastructure of the digital world is, to a remarkable degree, out in the open for anyone — including developers everywhere — to examine and improve.