If your server runs a current Debian, Ubuntu, or RHEL-family distro, your "iptables" rules are almost certainly already executing inside nftables. The iptables command has been a compatibility shim since 2019. The real question isn't which one wins; it's whether to keep writing rules in a legacy syntax on top of the new engine. This guide covers what actually changed architecturally, a side-by-side syntax comparison, what the honest performance data says, and a migration path that won't break Docker or lock you out.