C4 model for visualising software architecture is a lean graphical notation technique for modelling the architecture of software systems.

Apps for creating software architechture diagrams:

  • PlantUML allows to quickly write:
    • Sequence diagram
    • Usecase diagram
    • Class diagram
    • Object diagram
    • Activity diagram (here is the legacy syntax)
    • Component diagram
    • Deployment diagram
    • State diagram
    • Timing diagram
  • mermaid-js allows to quickly write:
    • Flowchart
    • Sequence diagram
    • Class Diagram
    • State Diagram
    • Entity Relationship Diagram
    • User Journey
    • Gantt
    • Pie Chart
    • Requirement Diagram

Simpler apps for creating more generic diagrams and charts: