If you’re building versioned docs for a REST API, the best tools depend on whether you want:

• API reference docs from an OpenAPI spec
• human-written docs / guides
• docs that support multiple API versions cleanly
• a docs site with search, navigation, auth examples, and code samples

Here are the main tools worth looking at:

1) OpenAPI-based documentation generators

Best if your API is already described in or can be described by OpenAPI.

Redoc / Redocly

• Great-looking API reference docs
• Strong support for OpenAPI
• Good for versioned docs via separate specs/versions
• Redocly adds more docs-site management features

Good for: polished reference docs and teams wanting a strong OpenAPI workflow.

Swagger UI / SwaggerHub

• The classic OpenAPI docs viewer
• Interactive “try it out” behavior
• SwaggerHub adds collaboration and version management

Good for: simple interactive reference docs.

Scalar

• Modern, clean OpenAPI docs experience
• Good developer UX
• Worth checking if you want a lighter, newer alternative

Good for: modern API reference docs with a nicer UI.

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2) Docs platforms with versioning built in

Best if you want both guides and reference docs, plus versioned content.

ReadMe

• Very popular for API docs
• Built-in versioning
• Supports guides, reference pages, changelogs
• Good developer portal features
• API explorer and examples

Good for: polished hosted docs and productized developer portals.

Stoplight

• OpenAPI design + docs + mock + governance
• Versioning support depending on setup
• Good for API-first teams

Good for: teams that want design, docs, and governance in one place.

GitBook

• Great for documentation sites
• Versioning support
• Better for guides than deeply interactive API refs
• Can work alongside OpenAPI tools

Good for: narrative docs, handbooks, and mixed docs sets.

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3) Static site generators + OpenAPI plugins

Best if you want full control and already use Markdown-based docs.

Docusaurus

• Excellent versioned documentation support
• Good for docs portals
• Can embed API reference via plugins or custom components
• Strong if you want docs and product docs together

Good for: versioned docs sites with flexibility.

MkDocs / Material for MkDocs

• Simple and elegant
• Strong versioning via plugins like mkdocs-material + versioning tools
• Great for technical docs
• OpenAPI integration is possible via plugins

Good for: clean, maintainable docs with Markdown.

Nextra / Next.js docs setups

• Highly customizable
• Good if your team is already in React/Next.js
• Versioning requires more setup

Good for: custom docs experiences.

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4) API documentation ecosystems

Useful when docs are tied closely to API lifecycle.

Apidoc / Slate

• More traditional docs generators
• Slate is nice for elegant manual API docs
• Less ideal if your API changes frequently and you want automatic syncing

Good for: curated documentation and smaller APIs.

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What I’d recommend by scenario

If you want the easiest “professional API docs” path:

• ReadMe or Redocly

If you want a docs site with strong versioning and lots of control:

• Docusaurus or MkDocs Material

If you want interactive OpenAPI reference docs only:

• Redoc or Swagger UI

If you want a modern hosted docs platform:

• ReadMe

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Key features to look for

For versioned REST API docs, make sure the tool supports:

• Multiple API versions side by side
• OpenAPI 3.x
• Code samples in multiple languages
• Authentication examples
• Try-it-out / API console
• Search
• Changelog / release notes
• Branching or preview environments
• Markdown support for guides and tutorials
• Custom domains and branding

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Practical recommendation

A very common and solid setup is:

• OpenAPI spec as the source of truth
• Redocly / ReadMe / Swagger UI for the reference docs
• Docusaurus or MkDocs for guides, tutorials, and versioned narrative content

If you want one tool to do most of it, ReadMe is often the most convenient. If you want maximum control and portability, Docusaurus + OpenAPI renderer is a strong choice.

If you want, I can also give you:

1. a comparison table of the top tools, or
2. a recommended stack based on your team size / budget / hosting preference.