# Chrome: This site can’t provide a secure connection — uses an unsupported protocol. ERR_SSL_VERSION_OR_CIPHER_MISMATCH

**Code:** `ERR_SSL_VERSION_OR_CIPHER_MISMATCH` · **Category:** Browser · **Seen on:** Chrome, Edge, Nginx, Apache

The browser and the server could not agree on a TLS version or cipher — the server is too old or misconfigured, or the browser is.

## Meaning

Modern Chrome needs TLS 1.2 or 1.3 with strong ciphers. Old servers offering only TLS 1.0/1.1 or weak RC4/3DES ciphers cannot connect; so can servers with a broken or missing certificate for the requested host. Owners should enable TLS 1.2+ and a modern cipher suite.

## Common causes

- Server supports only TLS 1.0/1.1 or weak ciphers
- SSL protocols disabled by a hardening change
- Missing or default certificate for the hostname (SNI)
- Outdated browser/OS
- Proxy or antivirus terminating TLS badly

## Quick fix

1. Owners: enable TLS 1.2/1.3 and a modern cipher list
2. Test the site with an SSL checker (Qualys SSL Labs)
3. Visitors: update the browser and OS, and test without antivirus HTTPS scanning

## Detailed fix by platform

### Nginx

1. `ssl_protocols TLSv1.2 TLSv1.3;` and `ssl_ciphers HIGH:!aNULL:!MD5;` then `nginx -t && systemctl reload nginx`

### Apache

1. `SSLProtocol -all +TLSv1.2 +TLSv1.3` in the SSL vhost

### Linux

1. Probe the server: `openssl s_client -connect example.com:443 -tls1_2` and `nmap --script ssl-enum-ciphers -p 443 example.com`

## How to diagnose

1. **Versions** — Which TLS versions does the server offer?
2. **Cert** — Valid certificate for this exact host?
3. **Client** — Old browser or OS?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/browser/err-ssl-version-or-cipher-mismatch)