# Chrome: This site can’t be reached — example.com unexpectedly closed the connection. ERR_CONNECTION_CLOSED

**Code:** `ERR_CONNECTION_CLOSED` · **Category:** Browser · **Seen on:** Chrome, Edge

The server closed the connection before finishing the TLS handshake or sending a response — typical for HTTP/HTTPS port mix-ups, strict firewalls and crashing servers.

## Meaning

Compared with "connection reset" (an abrupt RST), "closed" means a clean close during setup. Frequent causes are requesting https:// from a port that serves plain HTTP (or the reverse), a server that only supports newer TLS, a WAF dropping unknown clients, and antivirus HTTPS scanning.

## Common causes

- Using https:// on a port that serves only HTTP (or http:// on an HTTPS-only port)
- TLS version/cipher mismatch rejected by the server
- Firewall/WAF closing connections silently
- Antivirus or VPN interfering with TLS
- Server overloaded or crashed

## Quick fix

1. Check the URL scheme and port
2. Test with `curl -v` to see where it closes
3. Try without VPN/antivirus web protection

## Detailed fix by platform

### Linux

1. `curl -v https://example.com` and `openssl s_client -connect example.com:443 -servername example.com` show the handshake

### Windows

1. Temporarily disable "HTTPS scanning" in your antivirus; run `netsh winsock reset`

## How to diagnose

1. **URL** — Right scheme and port?
2. **Handshake** — Where does openssl s_client stop?
3. **Software** — Antivirus/VPN involved?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/browser/err-connection-closed)