If you've ever tried to apply for Google AdSense with a Next.js App Router site deployed on Vercel, you may have run into a frustrating issue: visiting your-domain.com/ads.txt returns a 500 Internal Server Error , even though the file exists in your public/ directory and works fine in local development.

This post explains why it happens and shares the cleanest fix I found while preparing my own site for AdSense submission.

The Problem

The conventional way to serve ads.txt is to drop it into the public/ directory.

In a Pages Router project, this works without issue.…