Redoc is Open Source
ReDoc uses the OpenAPI specification and generates a responsive site with a three-panel design. It pulls markdown headings from the OpenAPI description field into the side menu, and supports deep linking.
ReDoc aims to make deployment extremely easy, provides a wide support for OpenAPI objects, and offers interactive documentation for nested objects. You can include code samples via a third-party extension.
For Example:
https://redocly.github.io/redoc/
This link has instructions for installing and using Redoc: https://github.com/Redocly/redoc
redoc-cli bundle [spec] - bundles spec and ReDoc into zero-dependency HTML file.
To use in command line "redoc-cli bundle ./specs/api-description-v2.yml --output ./docs/index.html" it creates an html2 file