SSL Tools
TLS Version Checker
Check which TLS version and signature algorithm a website's server supports.
Enter a domain to check which TLS version its server negotiates.
Outdated TLS versions can hurt security and compliance - JustChecker keeps track of this for you automatically.
Frequently Asked Questions
It attempts to negotiate a connection using each TLS protocol version from legacy TLS 1.0/1.1 up through modern TLS 1.2 and 1.3, reporting exactly which ones your server is willing to accept.
Both have known cryptographic weaknesses and have been formally deprecated by major browser vendors and the IETF - PCI-DSS compliance for payment processing explicitly requires disabling them.
Supporting an old protocol version doesn't automatically mean active exploitation, but any client still using outdated software could be at risk. The standard practice is disabling TLS 1.0/1.1 entirely so only modern versions are negotiated.
TLS 1.3 removes outdated cryptographic options still permitted under 1.2 and reduces handshake round trips, improving both security and speed - but a correctly configured TLS 1.2 server with modern cipher suites is still considered secure.
Supporting a small range of modern versions (e.g. both 1.2 and 1.3) is normal, balancing compatibility with security. Supporting the full historical range including 1.0/1.1 is the actual concern this tool flags.
This is configured at the web server level (Apache, Nginx, IIS, or your load balancer/CDN), not via DNS or your certificate - consult your server software's SSL/TLS protocol configuration.
It can affect an extremely small, shrinking population of very old, never-updated browsers - for the overwhelming majority of modern traffic, disabling legacy protocols has no visible effect.