Can antivirus cause SSL errors?

Yes, antivirus HTTPS scanning (Avast, Kaspersky, Norton) intercepts TLS connections. This can cause errors if the antivirus uses outdated TLS settings.

How do I check a server's TLS version?

Use SSL Labs: ssllabs.com/ssltest. It shows the server's supported TLS versions, cipher suites, certificate chain, and security grade.

Chrome ERR_SSL_PROTOCOL_ERROR — SSL/TLS Handshake Failure

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Overview

Fix Chrome ERR_SSL_PROTOCOL_ERROR occurring when the SSL/TLS handshake between Chrome and the server fails due to protocol mismatch or certificate issues.

Key Details

ERR_SSL_PROTOCOL_ERROR means the TLS handshake failed before an encrypted connection was established
Chrome requires minimum TLS 1.2 — servers still using TLS 1.0/1.1 will fail
The error can occur due to misconfigured server certificates, cipher suites, or TLS settings
Corporate MITM proxies with outdated TLS support can trigger this error
Chrome's certificate transparency requirements can also cause this

Common Causes

Server using TLS 1.0 or 1.1 (deprecated, Chrome requires 1.2+)
Server cipher suite not matching any Chrome-supported ciphers
Misconfigured server SSL certificate (wrong chain, expired intermediate)
Corporate proxy intercepting HTTPS with an old TLS version
Antivirus HTTPS scanning interfering with the TLS handshake

Steps

1Check the server's TLS configuration: use ssllabs.com/ssltest to test the site
2Ensure your system clock is correct — wrong time causes certificate validation failure
3Disable antivirus HTTPS/SSL scanning temporarily to test
4Clear Chrome SSL state: Settings > Privacy > Security > Clear SSL state (Windows)
5Try another browser (Firefox) to determine if the issue is Chrome-specific or server-wide