Choosing the Right Diagram Tool
A practical guide to selecting the best diagram tool for your use case — comparing Mermaid, PlantUML, Graphviz, D2, Vega-Lite, and more.
This editor supports over a dozen diagram languages. Choosing the right one for your use case makes the difference between a diagram that takes five minutes to write and one that takes an hour.
Quick Decision Guide
Tool Comparison at a Glance
| Tool | Best For | Learning Curve | Output Quality |
|---|---|---|---|
| Mermaid | Flowcharts, sequences, Gantt | Low | Good |
| PlantUML | UML (class, sequence, use case) | Medium | Excellent |
| Graphviz | Graph structures, dependency trees | Medium | Excellent |
| D2 | Architecture overviews, system maps | Low | Excellent |
| Vega-Lite | Data charts (bar, line, scatter) | High | Excellent |
| Chart.js | Simple data charts | Medium | Good |
| C4 Model | Software architecture (C4 standard) | Medium | Excellent |
| ERD | Database entity relationships | Low | Good |
| Excalidraw | Hand-drawn style diagrams | Low | Unique |
| WireViz | Hardware wiring diagrams | Medium | Excellent |
| WaveDrom | Digital timing (electronics) | Medium | Excellent |
Mermaid — Best All-Rounder
Use Mermaid when: You want a quick, readable diagram with minimal syntax.
Mermaid supports flowcharts, sequence diagrams, Gantt charts, class diagrams, state diagrams, ER diagrams, and more — all in a concise, approachable syntax.
Limitation: Complex diagrams can become hard to layout precisely. Mermaid’s automatic layout works well for small-to-medium complexity.
PlantUML — Best for UML
Use PlantUML when: You are drawing formal UML diagrams (class, sequence, use case, component, deployment).
PlantUML is the most feature-complete UML tool available and produces very clean output. It is especially strong for sequence diagrams with complex interaction patterns.
Graphviz — Best for Graphs and Trees
Use Graphviz when: Your diagram is a pure mathematical graph: nodes and edges, dependency trees, call graphs, state machines.
Graphviz’s DOT language is terse and powerful. Its layout algorithms (dot, neato, fdp) produce optimal node placement automatically.
D2 — Best for Architecture Overviews
Use D2 when: You are drawing high-level system or cloud architecture diagrams where layout and style matter.
D2 produces visually polished diagrams with excellent automatic layout. Its SQL table syntax makes it useful for database schema visualisation too.
Vega-Lite — Best for Data Charts
Use Vega-Lite when: You have structured data (CSV, JSON) and need to visualise it as a chart (bar, line, scatter, histogram, heatmap).
Vega-Lite is a grammar of graphics — you describe what your data looks like and how to visually encode it, rather than manually drawing the chart.
Excalidraw — Best for Informal Sketches
Use Excalidraw when: You want a hand-drawn aesthetic that feels informal and exploratory. Great for whiteboard-style system sketches in presentations.
WaveDrom — Best for Electronics
Use WaveDrom when: You are documenting digital signal timing, bus transactions, or register bit-fields in electronics or FPGA design.
Summary Recommendations
| Scenario | Recommended Tool |
|---|---|
| General flowchart | Mermaid |
| API sequence diagram | Mermaid or PlantUML |
| UML class diagram | PlantUML |
| Software architecture | D2 or C4 Model |
| Dependency graph | Graphviz |
| Data visualisation | Vega-Lite |
| Database schema | D2 or ERD |
| Signal timing | WaveDrom |
| Informal sketch | Excalidraw |
| Hardware wiring | WireViz |