Explain the internal working of Swagger UI's rendering process?

Swagger UI is a client-side JavaScript application that fetches an OpenAPI document (as JSON, or YAML converted to JSON) and dynamically builds its entire interface from that document's structure, rather than shipping any pre-built, endpoint-specific HTML.

After fetching the document, Swagger UI resolves every $ref internally so that, by rendering time, it's working with a fully expanded in-memory model rather than following references live during rendering; it then groups operations under their declared tags, and for each operation, renders its parameters as a form, its schemas as expandable, syntax-highlighted structures, and its examples as selectable content.

Because the whole interface is generated dynamically from the document at load time, updating the API's documentation is purely a matter of updating the underlying OpenAPI document and reloading the page — there's no separate build step or static HTML regeneration required, which is part of why keeping the spec itself accurate is the single highest-leverage thing a team can do for documentation quality.