PlantUML
Leading#6 in Open sourcemedium confidence
The long-standing text-to-UML workhorse (~13.2k★) — most complete UML coverage, ubiquitous in enterprise toolchains despite dated visuals.Our read
Why it ranks #6
The long-standing UML workhorse at ~13.2k GitHub stars, ranked #3 in 2026 diagram-as-code comparisons and backed by decades of enterprise integrations despite a smaller GitHub footprint.Here is the catch
verbose syntax has a steeper learning curve than Mermaid or D2
local rendering requires Java or a PlantUML server
automatic layouts can be awkward and default visuals look dated
Does this well
broadest mature UML coverage among text-based tools
battle-tested integrations across enterprise IDEs and documentation systems
extensive standard-library icons for technical architecture
Pricing
Checked by hand on 2026-07-23. Prices in this category change often — if this looks wrong, it probably is.
Key features
comprehensive UML diagram coveragesequence, component, deployment and activity diagramslarge cloud and technology icon librariesIDE, wiki and CI integrations
Sources we read
Quick facts
More in this area
The rest of the Open source column.- 1MermaidThe 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.
- 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.
- 7C4-PlantUMLThe standard way to render C4-model software architecture diagrams as code (~7.4k★) — the go-to for C4 + text.