docs: add pageExtensions note to Middleware and clarify default filename (#84045)

Milancen123 · icyJoseph · web-flow · commit 2d96b9660fe8 · 2025-09-22T11:24:57.000+02:00
- Added a Note to the Middleware docs explaining that when `pageExtensions` are customized (e.g. `.page.ts`), the Middleware file should be named `middleware.page.ts` or `middleware.page.js`. - Updated wording so `middleware.ts/js` is described as the default filename, not a strict requirement.  --------- Co-authored-by: Joseph <joseph.chamochumbi@vercel.com>
diff --git a/docs/01-app/03-api-reference/03-file-conventions/middleware.mdx b/docs/01-app/03-api-reference/03-file-conventions/middleware.mdx
@@ -20,6 +20,8 @@ Middleware executes before routes are rendered. It's particularly useful for imp
 
 Create a `middleware.ts` (or `.js`) file in the project root, or inside `src` if applicable, so that it is located at the same level as `pages` or `app`.
 
+If you’ve customized [`pageExtensions`](/docs/app/api-reference/config/next-config-js/pageExtensions), for example to `.page.ts` or `.page.js`, name your file `middleware.page.ts` or `middleware.page.js` accordingly.
+
 ```tsx filename="middleware.ts" switcher
 import { NextResponse, NextRequest } from 'next/server'
 
