PlantUML

Mermaid

Mermaid is a simple markdown-like script language for generating diagrams and flowcharts from text. It can be used to create a variety of diagrams, including flowcharts, sequence diagrams, and Gantt charts. Mermaid is often used in documentation and can be integrated into various tools and platforms.

drawDB

drawDB is a web‑based tool that lets developers and DBAs create, edit, and share entity‑relationship diagrams directly in the browser. It supports forward and reverse engineering, letting you generate SQL from diagrams or import existing schemas. The platform is free, open‑source, and integrates with common version‑control workflows, making it ideal for collaborative schema design and documentation across teams.

d2

D2 is a concise scripting language that lets you generate diagrams directly from plain text. It focuses on simplicity and readability, making it easy to embed visualizations in documentation and codebases. Designed for self‑hosted environments, D2 runs in the browser and can be integrated into CI pipelines, providing free, on‑premise diagram generation without vendor lock‑in.