Choose between Mermaid and Graphviz DOT for technical diagrams, understand browser-rendering limits and export safe SVGs without executing pasted markup.
Why text-based diagrams are useful
A text definition can be reviewed in version control, copied into documentation and updated without moving shapes manually. It also makes large repeated diagrams easier to generate. The trade-off is that layout is determined by a renderer and may change when the engine or options change. Keep the source text with the exported image.
Where Mermaid fits
Mermaid uses approachable syntax and supports several documentation-oriented diagram types, including flowcharts, sequence diagrams and class diagrams. It is often convenient in Markdown systems that already support it. Not every hosting platform enables the same Mermaid release or security configuration, so test advanced syntax where the diagram will finally be published.
Where Graphviz fits
Graphviz DOT is strong for directed and undirected graphs and provides detailed control over nodes, edges, clusters and layout engines. It is useful for dependency maps, state relationships and architecture graphs. The language can be more explicit than Mermaid, and complex layouts may require experimentation with attributes.
Safe browser rendering
Diagram text should be treated as untrusted input. A browser editor must avoid executing raw HTML, scripts or event handlers embedded in labels or links. Exported SVG should be sanitised before reuse on another website. External image references and clickable URLs also deserve review, especially when a diagram came from an unknown source.
Choose based on the destination
Use the format already supported by the documentation platform when possible. Choose Mermaid for a quick readable diagram maintained with Markdown, and consider DOT when graph relationships or layout control are central. TXTNimble supports a practical local subset and reports parser limitations; it does not claim complete compatibility with every upstream feature or plugin.
Final review before relying on the result
Keep the original input, compare important values and use the destination system’s own validator or test environment. Privacy-first processing reduces unnecessary disclosure, but it does not replace access controls, professional review or a documented incident process. Use the related TXTNimble tool as a practical aid and record any limitation that affects the decision.
Keep diagrams maintainable
Store the source beside the documentation and review it like code. Use stable node identifiers, readable labels and comments where the language supports them. Split an overcrowded architecture into several focused views instead of forcing every relationship into one canvas. Pin or document the renderer version because layout and syntax support can change across releases.
Design for accessibility
A diagram should not be the only place where essential information appears. Add a caption and a text summary describing the main sequence or relationship. Use sufficient contrast, avoid relying only on colour and keep labels readable at common zoom levels. Export SVG for scalable documentation when the destination sanitises it correctly, and provide a raster alternative where required.
Review exported SVG carefully
SVG is XML and can contain links, external references or active content in unsafe configurations. Use a renderer in strict mode, prohibit raw HTML labels and sanitise the exported markup before publishing. Do not execute diagram text from an unknown source. If the destination platform reprocesses SVG, test the final uploaded result rather than assuming the local preview is identical.
A practical selection rule
Choose Mermaid when authors value concise documentation syntax and the destination already supports the diagram type. Choose Graphviz DOT when graph relationships, clusters or layout attributes need more control. For long-lived system documentation, prototype both with a representative diagram and compare readability, diff quality, export support and team familiarity. The best format is the one the team can safely maintain and validate.
Test the publishing workflow
Before standardising on a format, test editing, previewing, exporting and publishing with the actual documentation stack. Confirm that links, fonts, labels and accessibility text survive the process. A local preview is useful for drafting, but the final repository or content system remains the authoritative rendering environment.