An open-source content management system (CMS) is a software platform for building and managing websites that is developed collaboratively by a community of developers and made freely available to the public. The source code of the CMS is openly accessible, allowing users to view, modify, and distribute it according to the terms of its respective open-source license. Open-source CMS platforms provide flexibility, customization options, and community support, making them popular choices for individuals and organizations seeking cost-effective and adaptable solutions for website creation and management. Examples include WordPress, Joomla, Drupal, and many others.