How to use the OpenAPI sequence diagram generator

1. Paste an OpenAPI or Swagger spec
Drop OpenAPI 3.x YAML or JSON into the editor. The generator reads paths, methods, tags, and summaries to build sequence-style flows.
2. Review Mermaid output grouped by tag
Endpoints are grouped by OpenAPI tags so each API area becomes a readable sequence. Scan the generated Mermaid source in the preview panel.
3. Refine the generated diagram
Copy the Mermaid output into the sequence diagram editor to adjust participants, add error paths, or combine multiple tags into one narrative.
4. Share API behavior visually
Export diagrams for product specs, partner integrations, or internal microservice catalogs.

Common use cases

API onboarding
Help consumers understand call order across authentication, resource creation, and webhook callbacks.
Microservice catalogs
Turn machine-readable specs into human-friendly overviews for platform teams maintaining dozens of services.
Partner integration reviews
Walk external teams through expected client-to-API interactions without reading every path object manually.
Regression testing planning
Identify critical flows to cover in contract tests by seeing which endpoints cluster under the same tag.
Documentation refresh
Kick-start Mermaid diagrams for developer portals when migrating from Swagger 2.0 to OpenAPI 3.

Which OpenAPI versions work?: OpenAPI 3.x YAML and JSON are supported. Swagger 2.0 may parse when structure is compatible but OpenAPI 3 is recommended.
Does the generator model every response code?: The default diagram focuses on happy-path interactions grouped by tag. Edit the Mermaid output to add error branches.
Is my API spec uploaded?: No. Spec parsing happens locally in your browser.
Can I open the result in the Mermaid editor?: Yes. Copy or continue editing generated Mermaid notation in the sequence diagram editor for finer control.