rsnext/docs/api-reference/next.config.js/custom-page-extensions.md

description
Extend the default page extensions used by Next.js when resolving pages in the pages directory.

Custom Page Extensions

Aimed at modules like @next/mdx, which adds support for pages ending with .mdx. You can configure the extensions looked for in the pages directory when resolving pages.

Open next.config.js and add the pageExtensions config:

module.exports = {
  pageExtensions: ['mdx', 'jsx', 'js', 'ts', 'tsx'],
}