Visitors can't fix the site's encryption themselves. Check the clock, update Chrome and try another network. If the site still fails, it is using outdated TLS. Site owners must enable TLS 1.2/1.3, use modern ciphers, and install a certificate that covers the exact hostname.

What ERR_SSL_VERSION_OR_CIPHER_MISMATCH means

During the HTTPS handshake, the browser lists the TLS versions and ciphers it supports and the server picks one. ERR_SSL_VERSION_OR_CIPHER_MISMATCH (“example.com uses an unsupported protocol”) means there was no overlap.

Chrome removed TLS 1.0 and 1.1 and weak ciphers years ago, so old devices, routers, printers and neglected websites are the usual sources. Some CDNs also show it when a certificate hasn’t been issued yet for a newly added hostname.

What you'll see

  • “This site can’t provide a secure connection. Example.com uses an unsupported protocol.”
  • The client and server don't support a common SSL protocol version or cipher suite.
  • Often seen on old router admin pages, NAS boxes or legacy intranet sites.

Why ERR_SSL_VERSION_OR_CIPHER_MISMATCH happens

  • Server allows only TLS 1.0/1.1 or obsolete ciphers (RC4, 3DES).
  • Certificate missing or not yet provisioned for that hostname (common right after adding a domain to a CDN).
  • Antivirus or proxy re-encrypting traffic with outdated settings.
  • A very old browser or operating system.

How to fix it

  1. Update ChromeOpen chrome://settings/help to update to the latest version and relaunch.
  2. Try another network and pause HTTPS scanningLoad the site on mobile data and with antivirus HTTPS scanning turned off, to rule out interception.
  3. For old local devicesUpdate the device's firmware. Many routers and printers gained TLS 1.2 support in later updates. If none exists, use the device's HTTP page on a trusted network only.
  4. Site owners: modernise TLSEnable TLS 1.2 and 1.3, disable TLS 1.0/1.1, and use AEAD cipher suites (AES-GCM, ChaCha20-Poly1305). Test with an online SSL checker.
  5. Site owners: check the certificateMake sure the certificate covers the exact hostname (including www) and, on a CDN, that edge certificates show as active.
How to confirm the fix: The site loads with a padlock and the connection details show TLS 1.2 or 1.3.

Stop it happening again

Site owners should review TLS settings yearly and enable automatic certificate renewal.