Draw.io is a free online diagramming and whiteboarding application that allows users to create and edit diagrams directly in their web browser. The application is developed and maintained by a core team and is available under the Apache License 2.0. Draw.io can be used as a lightweight alternative to other diagramming tools and has features such as customizable icon sets and stencil libraries. The application also has a desktop version and can be self-hosted using Docker.