Tim Vereecke at performance.sync()
summary
Claim: unattributed navigation overhead (UNO) often adds seconds to Time to First Byte because RUM drops cross‑origin redirects and service worker startup. Measured values: P10 ~8 ms, P75 ~421 ms on one site, but a customer shows P75 in the seconds (4–6 s) range caused by ad‑server redirect chains; removing one publisher path saves ~2.5–5 s. Fixes implemented: capture redirects in RUM, increase DNS TTL, move to TLS 1.3, and reconfigure ad server behavior.
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