DNS Lookup Time: Measure Network Latency with curl

Question: How do I measure DNS lookup, connect, and download time separately?

Try:
curl -w '@-' -o /dev/null -s https://google.com <<'EOF'
  time_namelookup: %{time_namelookup}s
  time_connect: %{time_connect}s
  time_appconnect: %{time_appconnect}s
  time_pretransfer: %{time_pretransfer}s
  time_starttransfer: %{time_starttransfer}s
  time_total: %{time_total}s
EOF

Info: curl -w customizes output formatting using predefined variables. Breaking down latency identifies bottlenecks across DNS resolution, TCP handshakes, TLS negotiation, and server response times. This makes it easier to measure DNS lookup time separately from other connection stages.

Examples:

• $ curl -w 'HTTP: %{http_code}, Time: %{time_total}s\n' -o /dev/null -s https://example.com  # Check status code and total duration
• $ curl -w '%{time_total}\n' -o /dev/null -s -X POST -d 'data' https://api.example.com  # Benchmark API response speed
• $ curl --resolve example.com:443:1.2.3.4 https://example.com  # Test direct IP routing, bypassing DNS

Note: High appconnect indicates TLS handshake delays, high starttransfer indicates server processing lag (TTFB), and high connect signals network routing latency.