The technology that made dedicated IPs unnecessary for SSL.
THE OLD PROBLEM
A server presents its certificate before the browser says which site it wants. With many sites on one IP address, the server could not know which certificate to present, so each secure site needed its own address.
WHAT SNI CHANGED
Server Name Indication lets the browser state the hostname at the start of the connection, before the certificate is presented. The server then presents the correct one.
WHERE IT IS SUPPORTED
Every browser and operating system in current use. It has been universal for years.
WHAT THIS MEANS
SSL works perfectly on shared IP addresses. The advice that a dedicated IP is required for SSL is obsolete and has been for a decade, though it persists in older articles.
WHEN IT MATTERS
Only with extremely old clients that predate SNI support, which in practice means systems that cannot connect to most of the internet anyway.
IF SOMEONE TELLS YOU OTHERWISE
Ask them what specifically requires it. Usually it is repeated advice rather than a real constraint.
