If you don't comply, your website won't be recognized by Chrome.
Infosecurity Magazine Explains:
Google is making its Certificate Transparency initiative mandatory for website certs issued from October 2017, in a bid to further improve stability and security on the internet.
In a note online this week, software engineer Ryan Sleevi, clarified that any new certs issued after that time would not be recognized by Chrome.
“This is a significant step forward in the online trust ecosystem. The investments made by CAs adopting CT, and Chrome requiring it in some cases, have already paid tremendous dividends in providing a more secure and trustworthy internet,” he explained.
“The use of Certificate Transparency has profoundly altered how browsers, site owners, and relying parties are able to detect and respond to mis-issuance, and importantly, gives new tools to mitigate the damage caused when a CA no longer complies with community expectations and browser programs.”
