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HTTP/1.1 head-of-line blocking and the 6-connection-per-host limit dictate why your site loads fonts in waves; HTTP/2 multiplexing fixes one HOL blocking layer but TCP retransmits still stall every stream. HTTP/3 over QUIC is now standard on every major CDN and has different debugging tools — Wireshark won't decode QUIC payloads without keylogs.
Inspect which HTTP versions a cloud load balancer negotiates per request.
--http1.1, --http2, --http3 — record which the server actually returns.alt-svc response header on an HTTP/2 response — note the h3 advertisement that triggers QUIC for the next visit.curl -Z.Use these three in order. Each builds on the one before.
In one paragraph, explain the practical difference between HTTP/1.1, HTTP/2, and HTTP/3 like I'm new to it.
Walk me through how HTTP/2 multiplexing works on a single TCP connection and why a single packet loss still causes a stall.
Given a video streaming app on flaky 4G, argue whether HTTP/3 is worth the migration cost — quantify the win in terms of HOL blocking and connection setup time.
# Force HTTP/1.1
curl -v --http1.1 https://example.com -o /dev/null 2>&1 | grep -i "HTTP/"
# Force HTTP/2 (negotiated via ALPN)
curl -v --http2 https://example.com -o /dev/null 2>&1 | grep -i "HTTP/"
# CloudFront supports HTTP/3; check distribution config
aws cloudfront get-distribution-config --id <dist-id> \
--query 'DistributionConfig.HttpVersion'
# Probe HTTP/3 support
curl --http3 https://cloudflare.com -o /dev/null -w "%{http_version}\n"