Definition. A CMS whose source code is available under an open source licence and that can be installed, operated and customised without proprietary licence fees. Well-known examples are TYPO3, Drupal, WordPress and Strapi. The term says nothing about maturity, security or support options. These depend on the specific project.

Why it matters. For mid-sized companies, an open source CMS is a pragmatic choice when maintainability, customisability and independence from suppliers are on the list, provided the team or a service provider can maintain the system over the long term.

Related. Open Source, TYPO3, Enterprise CMS, Headless CMS, AI-ready CMS