1. Built for Different Purposes: Docusaurus is primarily a documentation tool, designed to help developers build and maintain documentation websites. It provides a framework and easy-to-use tools for creating and organizing documentation, with a focus on open source projects. On the other hand, ReadMe.io is a broader platform that offers API documentation, developer portals, and other features beyond just documentation.
2. Hosting and Deployment Options: Docusaurus websites can be deployed using static site generators like GitHub Pages or Netlify, which offer free hosting options. ReadMe.io, on the other hand, provides its own hosting and deployment infrastructure, making it easier for users to publish and manage their documentation without relying on third-party services.
3. Customization and Theming: Docusaurus offers a wide range of customization options, allowing users to create a unique look and feel for their documentation websites. It provides a theming system that enables users to modify the design, layout, and colors of their websites. ReadMe.io, although it allows some customization, its options are more limited compared to Docusaurus.
4. Frontend Framework Support: Docusaurus is built with React.js, a popular JavaScript library for building user interfaces. This means that developers familiar with React will find it easier to work with Docusaurus and leverage its component-based architecture. On the other hand, ReadMe.io uses a different stack and does not have direct integration with React or any other frontend framework.
5. Community and Ecosystem: Docusaurus has a thriving community of developers, which means that users can benefit from community-contributed plugins, themes, and extensions. Additionally, because Docusaurus is open source, users can contribute to its development and help shape its future. ReadMe.io, although it has its own community, is more focused on providing a complete solution rather than community-driven extensions.
6. Pricing Model: Docusaurus is an open source tool and completely free to use, making it an attractive choice for projects with limited budgets. On the other hand, ReadMe.io offers various pricing tiers, including free and paid plans, depending on the specific needs and requirements of the users.

In summary, Docusaurus is a documentation tool with extensive customization and theming options, built on React.js, and supported by a vibrant community. It is free and offers flexibility in hosting options. ReadMe.io, on the other hand, is a comprehensive platform that provides not only documentation solutions but also features like API documentation, developer portals, and its own hosting infrastructure, with more limited customization options and a different pricing model.