This tool replaced every diagramming app I've ever used

Mermaid is a free, open-source, JavaScript-based diagramming tool that generates diagrams from plain text syntax. Instead of dragging and dropping shapes, users write simple commands like 'A --> B' to produce flowcharts, mind maps, and decision trees. The syntax is beginner-friendly and well-documented, making it accessible to non-coders. Diagrams are infinitely editable by changing a few lines of text, and Mermaid integrates natively into tools like Notion and Obsidian. It requires no sign-up and offers all core features for free, with paid tiers limited to collaborative features.