Israeli researchers eavesdropped on encrypted web traffic on their own network. They were able to guess which combination of operating system, browser and web service were in play. They could guess fairly reliably that this user was watching YouTube using Safari on OS X, while that user was using Twitter from Internet Explorer on Windows. That might not sound like a terribly important or worrying result, but remember that TLS encryption is supposed to provide confidentiality. In other words, anything that leaks out about whats inside a TLS-protected data stream is information that an eavesdropper isnt supposed to be able to figure out.”]
Source: https://nakedsecurity.sophos.com/2016/03/18/what-your-encrypted-data-says-about-you/