Enabling HTTP/3 (QUIC) in browsers for improved network performance

Back in 2015, Google introduced SPDY as a method of improving TCP connections. HTTP/3 now improves upon that by removing the blocking of TCP with the use of UDP (QUIC).

Firefox: currently disabled by default in version 85, to enable use about:config and set network.http.http3.enabled = true

IOS Safari 14+: currently disabled by default, but can be enabled under Settings > Safari > Advanced > Experimental Features > HTTP/3

Chrome/Chromium: current versions 88+ are currently implementing by default.

Chromium Edge: as new versions are based upon Chromium, support should follow Chrome.

MSIE: was never and will never be implemented.

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HTML5 preconnect

In addition to dns-prefetch, you can take browser performance one step further by actually creating a new connection to a resource.

By initiating an early connection, which includes the DNS lookup, TCP handshake, and optional TLS negotiation, you allow the user agent to mask the high latency costs of establishing a connection.

Supported in:

  • Firefox 39+ (Firefox 41 for crossorigin)
  • Chrome 46+
  • Opera


<link rel="preconnect" href="//example.com" />
<link rel="preconnect" href="//cdn.example.com" crossorigin />

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