Not all versions of the protocol are safe.
THE VERSIONS
- TLS 1.0 and 1.1: obsolete and disabled by all current browsers. Known weaknesses.
- TLS 1.2: widely supported and secure. The current baseline.
- TLS 1.3: the newest, faster and simpler. Supported by all current browsers.
WHAT THIS MEANS FOR YOU
Modern servers offer TLS 1.2 and 1.3 and refuse the older versions. Visitors on current browsers connect without issue.
Visitors on very old browsers or operating systems may be unable to connect at all. This is deliberate; supporting obsolete protocols to accommodate them would weaken security for everyone.
WHEN IT CAUSES PROBLEMS
An old payment terminal, an embedded device, or a legacy application connecting to your API may only support an obsolete version. The fix is to update that system, not to weaken your server.
Some old mail clients hit the same issue. Updating the client resolves it.
CHECKING
Online SSL testing tools report which versions your server offers and grade the configuration.
