More and more people are now getting IPv6-only connections (notably on mobile). To access IPv4-only websites, the ISP is using "carrier-grade NAT". Therefore, i

More and more people are now getting IPv6-only connections (notably on mobile). To access IPv4-only websites, the ISP is using "carrier-grade NAT". Therefore, if your website is IPv4-only, users will go through a big translation cluster. The incentive for an ISP to keep it running well will become lower with time: the most "important" websites are accessible through IPv6. If you are IPv4-only, you will provide some of your users suboptimal service because the CGNAT box may slow down connections, drop connections or loose packets.