jeffbailey.us
Structurizr vs Mermaid vs PlantUML for C4 Diagrams
Three tools draw C4 diagrams from text, and picking between them looks like a taste question about syntax. It is mostly a question about what you want to keep: a picture, or a model that can produce pictures.
Everything below was run on one system modeled three ways, with Structurizr 2026.09.19 (structurizr-* 6.2.3), Mermaid CLI 11.17.0 on mermaid 11.17.2, and PlantUML 1.2026.8 on Graphviz 16.1.0.
## The short answer
**Reach for Structurizr** When the same system needs more than one diagram. You describe the model once and generate every view from it, so a renamed container changes in one place.
**Reach for Mermaid** When the diagram must render where it lives, in a README or a wiki, with no build step and no renderer to install.
**Reach for PlantUML** When layout quality matters most. Graphviz routes edges around boxes, and no other option here does.
These are not three competitors for one slot. Structurizr exports PlantUML and Mermaid, so the real choice is whether you keep a model upstream of whichever renderer you already use.
![[image description: a poem embedded in an Excel spreadsheet with the words contained within individual cells. Line 3 has words in a single merged cell. Line 4 has text wrapping applied. Line 8 has filters applied to each word]
Love Excels
Let’s spread ourselves on sheets of love
and turn our data into poetry.
Our cells shall merge themselves together
As you wrap your text around me.
Our sum is greater than our parts,
let’s crunch our figures without compunction.
Remove this filter from my heart –
you give me form and function.
We shall frolic among the formulae,
pivot our tables now and often.
I will total all your rows
and you can add my column.
Brian Bilston](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:3hptt3d3jvwahhnl3jvsycc2/bafkreiaa4kywxfiv3gdsj66zt6tuoja2kjwhi6tctwayydltiq54if6wmu)