Next.js Incremental Static Regeneration (ISR) is a hybrid rendering strategy introduced in version 9.5 that combines the benefits of static site generation (SSG) and server-side rendering (SSR) to deliver both high performance and content freshness. ISR allows static pages to be updated after deployment without requiring a full rebuild, by regenerating pages in the background at specified intervals. This approach is particularly beneficial for content-heavy sites like ecommerce platforms, blogs, and news websites. Implementing ISR involves using time-based or immediate revalidation strategies, which require hosting on compatible platforms like Vercel or Netlify. The guide also addresses common issues and best practices, such as choosing appropriate revalidation intervals and optimizing data fetching. For users of Contentful, ISR can be integrated using webhooks to trigger page regeneration upon content updates, enhancing the overall digital experience.