C4 Modeling Tool

Create and maintain C4 models for your software architecture

Viaduct is a C4 modeling tool for software teams that need architecture documentation to remain clear, structured, and up to date. Draw system context, container, component, and code diagrams — and keep them in sync with how your software actually works.

All four C4 levels

L1 — System Context: who uses your software and what external systems it talks to
L2 — Container: deployable units — web apps, APIs, databases
L3 — Component: internal structure of a container
L4 — Code: class-level detail where it matters

Who it's for

Software architects, tech leads, and engineering teams that use the C4 model — or want to start. If you've used Structurizr, C4-PlantUML, or drawn C4 diagrams in draw.io, Viaduct is a team-ready alternative that doesn't require code to update.