Kroki
Kroki is a unified, open source diagram-as-code rendering service that provides a single REST API endpoint for generating diagrams from text-based definitions across more than 25 different diagramming languages and notations. Instead of integrating separate tools and libraries for each diagram type, developers use a single Kroki endpoint and specify the diagram type — Kroki routes the rendering to the appropriate engine behind the scenes.
The supported diagram types span the full range of technical and business diagramming needs: Mermaid for flowcharts, sequence diagrams, Gantt charts, and class diagrams; PlantUML for UML sequence, activity, component, and state diagrams; Graphviz DOT for general-purpose directed and undirected graphs; C4 for software architecture context, container, and component diagrams; D2 for declarative diagramming with an elegant syntax; BPMN for business process modeling; ERD for entity relationship diagrams; and many others including Excalidraw, BlockDiag, NwDiag, and WaveDrom.
The API interface is simple and consistent. For a POST request, send the diagram source as the request body with the diagram type and output format in the URL path. For GET requests, the diagram source is base64-encoded and included in the URL — making it possible to embed live-rendered diagrams directly in Markdown documents using standard image syntax without any backend infrastructure.
Output formats include SVG (scalable vector graphics, ideal for web embedding and documentation), PNG (raster format for presentations and exports), and PDF (for document generation). SVG output is particularly valuable because the diagrams scale perfectly at any size and can be styled with CSS.
The diagram-as-code approach transforms how Nigerian engineering teams manage technical documentation. When architecture and flow diagrams are stored as text definitions in version control alongside the source code they describe, they stay in sync with the code — reviewable in pull requests, diffable, and updatable without needing diagram software. This is a significant improvement over binary diagram files (Visio, Lucidchart exports) that cannot be meaningfully reviewed or versioned.
For Nigerian startups and technology companies building engineering culture and documentation practices, Kroki provides a foundation for maintainable technical documentation. Architecture diagrams, API flow diagrams, database schemas, and deployment topology diagrams can all be maintained as text and rendered on demand.
Nigerian technical writers, developer advocates, and documentation teams can embed Kroki-rendered diagrams in documentation sites, wikis, and READMEs by embedding the Kroki URL as an image source. The diagram renders live from its source definition — no image export, upload, or file management required.
The service is completely free to use via the public kroki.io instance, with no API key or registration required. For organizations with data privacy requirements or reliability needs, Kroki can be self-hosted using Docker, giving full control over the rendering infrastructure. This makes it ideal for Nigerian organizations with strict data handling requirements.
Since Kroki is open source under the MIT license, Nigerian developers can inspect the source code, contribute improvements, or fork and adapt it for specific needs. The project is actively maintained and continuously adds support for new diagram types as they gain adoption in the developer community. Kroki's Docker image bundles all diagram rendering engines together, so a self-hosted instance provides all 25+ diagram types without separate installation of each diagramming tool. Nigerian teams deploying Kroki internally get the full diagram catalog from a single container, with no additional software installation required.