Read docs Updated 2026-06-17
What is Kroki?
Kroki is a lightweight HTTP service that renders diagrams from textual input using backends such as PlantUML, Mermaid, Graphviz and others.
It is useful for documentation pipelines, static site generators and any workflow that needs on-demand diagram generation without local diagram software.
What you can build with Kroki
Embed diagrams in technical documentation
Convert PlantUML, Mermaid or Graphviz source stored in Markdown files into PNG/SVG images during static site builds.
Generate architecture diagrams in CI pipelines
Include Kroki calls in GitHub Actions or GitLab CI to automatically render and attach diagrams to pull-request comments or release notes.
Render user-supplied diagrams in web apps
Accept diagram source from users via a textarea and display the resulting image without running any diagramming libraries on the server.
Get started with Kroki
- 1Pick a supported diagram type (e.g. mermaid, plantuml) and write the textual description
- 2URL-encode the source and append it to https://kroki.io/{type}/{format}
- 3Issue a simple GET request (no headers or auth needed)
- 4Embed the returned image URL directly in HTML or download the binary
- 5Optionally switch to POST with JSON body for longer diagrams
Kroki: pros & cons
Pros
- +No API key or registration required
- +Single HTTPS endpoint for dozens of diagram languages
- +Returns ready-to-use PNG, SVG or PDF
- +Lightweight integration with any HTTP client
Cons
- –Depends on public Kroki instance availability
- –Large or complex diagrams may hit size/time limits
- –Only image output; no interactive editing
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Frequently asked questions
A free public service that renders text diagram descriptions into images using many popular diagramming tools through one unified endpoint.
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