getStaticPaths is a Pages Router function that defines which dynamic routes should be pre-rendered as static pages at build time
getStaticPaths is a special async function used alongside getStaticProps in the Next.js Pages Router (pages directory) for dynamic routes (like pages/blog/[slug].js). It specifies which path parameters should be pre-rendered as static HTML at build time. The function returns an array of possible parameter values, and Next.js then calls getStaticProps for each path to generate the corresponding static page. Like getStaticProps, this function is not available in the App Router, where it has been replaced by generateStaticParams.
paths (required): An array of objects that define which paths to pre-render. Each object must have a
paramsproperty containing the dynamic route parameters (e.g.,{ params: { slug: 'hello-world' } }) .fallback (required): Controls what happens for paths not returned in
paths. Can befalse,true, or'blocking'.For catch-all routes like
pages/[...slug].js, params should be an array:{ params: { slug: ['a', 'b'] } }for the path/a/b.
The fallback option is crucial for balancing build time and user experience. With fallback: false, any paths not returned by getStaticPaths will result in a 404 page, ideal for sites with a fixed set of content. With fallback: true, a fallback version of the page is shown immediately while the full page is generated in the background, after which it's cached. With fallback: 'blocking', users wait for the server to generate the page before seeing anything, useful for SEO where you don't want a loading state but need on-demand generation .
Build Time Impact: The more paths you return, the longer your build takes. For large sites, use fallback strategies and pre-render only popular content .
Context Parameter:
getStaticPathsreceives acontextobject with properties likelocalefor i18n routing, allowing you to generate paths for multiple locales .Not Available in Client:
getStaticPathsruns only during build or on-demand generation, never in the browser .Required for SSG with Dynamic Routes: You must export
getStaticPathsfrom a dynamic page if you're usinggetStaticProps.App Router Alternative: In the App Router, use
generateStaticParamswhich returns an array of params objects without needing to specify fallback separately .
In the App Router, getStaticPaths is replaced by generateStaticParams, which is simpler to use. Instead of returning a paths array with nested params objects, you return a flat array of parameter objects directly. Fallback behavior is handled separately with dynamicParams export. This makes the API more intuitive while providing the same functionality .