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# Why Vercel custom domains return ERR_CONNECTION_CLOSED on trailing dot FQDN

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Yuze (@yuzeguitarist) · 2026-03-22

## Domain
`deckclip.app` (production custom domain on Vercel)

## Problem
Visiting `https://deckclip.app./` (FQDN with a **trailing dot**) fails in Chrome with `ERR_CONNECTION_CLOSED` — the connection drops before any HTTP response. `https://deckclip.app` (no trailing dot) works normally.

## Current vs Expected Behavior
- **Current:** TLS does not complete when the client uses the trailing-dot form; browser shows connection closed.
- **Expected:** Edge should treat `deckclip.app.` the same as `deckclip.app` for TLS `SNI` / host matching (normalize by stripping a trailing dot), similar to large public sites, then serve or redirect as usual.

## Why Configuration Doesn't Fix It
This fails at **TLS**, so `vercel.json` redirects never run.

## Steps to Reproduce

**Browser:** Open `https://deckclip.app./` → `ERR_CONNECTION_CLOSED`.

**CLI (openssl):**

```bash
# Trailing dot in SNI — fails / no cert
echo | openssl s_client -connect deckclip.app:443 -servername 'deckclip.app.'

# No trailing dot — succeeds
echo | openssl s_client -connect deckclip.app:443 -servername 'deckclip.app'
```

## Project Details
Static site on Vercel (Next.js **static export**). Framework details are secondary; the issue reproduces purely at TLS/`SNI` against the custom domain.

## Request
Can Vercel normalize trailing-dot FQDN hostnames at the edge for `SNI` and routing?

Thanks.


system (@system) · 2026-03-22

The domain troubleshooting guide can help with most custom domain configuration issues. You might be able to use that guide to solve it before a human is available to help you. Then you can come back here and share the answer for [bonus points](https://community.vercel.com/t/introducing-the-vercel-leaderboard/1358).

https://vercel.com/docs/projects/domains/troubleshooting

You can also use [v0](https://v0.dev/) to narrow down the possibilities.