Strapi v4 introduces a major release with significant changes, including a new Plugin API, which requires developers to follow a migration guide to upgrade plugins from v3 to v4. This guide provides detailed steps and tools, such as codemods, to automate parts of the migration process by adjusting folder structures, updating imports to scoped packages, and modifying plugin configurations and lifecycle functions. The migration also involves renaming models to content types, updating relational attributes, and restructuring entry files like `strapi-server.js` and `strapi-admin.js`. Developers are encouraged to register plugins with new methods, use React components for icons, and integrate with Strapi's new lifecycle functions, such as `register()` and `bootstrap()`. Additional resources are provided for further customization, including API references and the upcoming Strapi Market, which aims to foster community contributions. The guide also highlights the importance of verifying the updated plugin's functionality before finalizing the migration.