The headline new feature is TLSv1.3. This new version of the Transport Layer Security protocol was published by the IETF just one month ago as RFC8446. This is a major rewrite of the standard and introduces significant changes, features, and improvements which have been reflected in the new OpenSSL Version.

What's more is that OpenSSL 1.1.1 is API and ABI complaint with OpenSSL 1.1.0 so most applications that work with 1.1.0 can again of many benefits of TLSv 1.3 simply by dropping in the new OpenSSL Version. Since TLSv1.3 works very differently to TLSv 1.2 though there are a few caveats that may impact a minority of applications.