Warm up DNS/TLS for required cross-origin hosts early with preconnect or dns-prefetch.
Establishing a connection to a new origin costs DNS + TCP + TLS round trips; doing it early hides that latency.
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Each new origin (fonts, CDN, analytics) needs DNS, TCP, and TLS handshakes before the first byte. preconnect does this work ahead of the request instead of on the critical path.
<!-- bad: connection set up only when the asset is requested -->
<script src="https://cdn.example.com/lib.js"></script>
<!-- good: warm the connection in <head> first -->
<link rel="preconnect" href="https://cdn.example.com" crossorigin />Reserve preconnect for a few truly critical origins; use dns-prefetch for the rest to avoid contention.