Next 12 introduces a new feature called [Middleware](https://nextjs.org/docs/middleware), in which functions

run before a request has finished processing. Middleware can be used to modify the request or replace the response. For

example, it can change headers, rewrite the request path, or return a different response entirely.

Next.js Middleware can run either in an edge function or at the origin. On Netlify, middleware runs at the origin as part

of the normal Next.js server.

When running at the origin, Next.js does not populate the `request.geo` object. Fortunately there is a one line fix to get

the visitor's country:

Because the middleware runs at the origin, it is run _after_ Netlify rewrites and redirects. If a static file is served by the Netlify CDN

then the middleware is never run, as middleware only runs when a page is served by Next.js. This means that middleware should not be used with the

before any middleware can be run.

There is currently [a bug in Next.js](https://github.com/vercel/next.js/issues/31179) that causes a proxy loop if you

try to rewrite to a URL with a host other than localhost. If you are using a pattern like this:

// Change the `nextUrl` property in some way

req.nextUrl = req.nextUrl.replace('something', 'somethingelse')

// ...then rewrite to the changed URL

return NextResponse.rewrite(req.nextUrl)

}

...then you need to set the `nextUrl.host` to `localhost`:

export function middleware(req: NextRequest) {

// Change the `nextUrl` property in some way

req.nextUrl = req.nextUrl.replace('something', 'somethingelse')

req.nextUrl.host = 'localhost'

return NextResponse.rewrite(req.nextUrl)

If you have an issue with Next.js middleware on Netlify while it is beta, particularly if the issue cannot be reproduced when

running locally, then please add a comment to [the Next plugin beta discussion](https://ntl.fyi/next-beta-feedback).