Mermaid
Leading#1 in Open sourcehigh confidence
The de-facto text-to-diagram standard (~89.4k★) — natively rendered in GitHub/GitLab Markdown, making it the default diagram-as-code format agents produce for architecture, flow and sequence diagrams.Our read
Why it ranks #1
The default diagram-as-code standard at ~89.4k GitHub stars, native rendering in GitHub/GitLab and most documentation platforms, and the #1 recommendation in 2026 diagram-as-code comparisons.Here is the catch
layout control is limited and nodes cannot be positioned precisely
large diagrams become difficult to read in source and rendered form
syntax mistakes can break rendering and architecture-specific icon support is limited
Does this well
largest ecosystem and widest native integration support in diagram-as-code
plain-text diagrams version and review cleanly with source code
low barrier for common flow, sequence and architecture diagrams
Pricing
Checked by hand on 2026-07-23. Prices in this category change often — if this looks wrong, it probably is.
Key features
30+ text-defined diagram typesnative Markdown and documentation renderingthemes and automatic layoutbrowser, npm and CLI rendering
Sources we read
Quick facts
More in this area
The rest of the Open source column.- 2ExcalidrawThe dominant open-source virtual whiteboard (~128.3k★) — hand-drawn aesthetic, hugely used for freeform architecture sketches and system diagrams.
- 3Diagrams (mingrammer)The leading diagram-as-code library for cloud/system architecture (~42.5k★) — draw AWS/GCP/Azure/Kubernetes architecture from Python.
- 4D2Fast-rising modern diagram scripting language (~24.8k★) — cleaner syntax than PlantUML with strong automatic layout.
- 5tldrawInfinite-canvas whiteboard SDK (~49.2k★) — the toolkit developers build collaborative diagramming apps on.
- 6PlantUMLThe long-standing text-to-UML workhorse (~13.2k★) — most complete UML coverage, ubiquitous in enterprise toolchains despite dated visuals.
- 7C4-PlantUMLThe standard way to render C4-model software architecture diagrams as code (~7.4k★) — the go-to for C4 + text.