Open source

Open source describes software whose source code is available under a license granting defined rights to use, inspect, modify, and redistribute it.

Plan for this page

Understand one concept in plain language and connect it to nearby ideas.

You will leave with: The exact rights and obligations come from the license, including attribution, notice, patent, or reciprocal-sharing terms. Publicly viewable code without an appropriate license is not automatically open source.
Time: 3–8 min
Before you begin: No prerequisite. Keep one real example in mind.
Do this now: Read the explanation, then compare the example with the common misunderstanding.

Prepared next stepExamine openness and AI systems

Open sourceOpen source describes software whose source code is available under a license granting defined rights to use, inspect, modify, and redistribute it.

Transparency
Open model
API

Plain explanation

The exact rights and obligations come from the license, including attribution, notice, patent, or reciprocal-sharing terms. Publicly viewable code without an appropriate license is not automatically open source.

Example

A library publishes its code with a named license, contribution history, documentation, and the terms under which modified versions may be distributed.

Why it matters

Open-source software can support inspection, adaptation, collaboration, and portability, but openness does not guarantee quality, security, maintenance, neutrality, or an unrestricted model.

Common misunderstanding

Misconception: free to download means open source. Correction: price and licensing are different; the license must grant the relevant source-code rights.

Related concepts

Follow relationships, not only the alphabet

TransparencyTransparency is making relevant information about a system, its use, evidence, limits, and governance available to the people who need it.Open modelAn open model is a model for which selected artifacts and usage rights are made publicly available, with the degree of openness stated explicitly.APIAn API, or application programming interface, is a defined way for software components to request functions or exchange data.

Examine openness and AI systems

Sources and scope

What supports this object

Stanford AI Index Report 2026Stanford Institute for Human-Centered AI

Provides dated evidence on AI development and industry ecosystems; it is not a software-licensing authority, so item-level license terms remain controlling.

Open source

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