Engineering · May 27, 2026 · 9 min read
Core Web Vitals in 2026: what actually moves the needle
INP replaced FID, attention shifted to interaction latency, and half the classic advice went stale. The fixes that carried our client sites to green this year.
Every performance audit we run starts the same way: field data first, lab data second, opinions last. Here's what the field data has been saying across our client portfolio this year.
INP is where sites fail now
Loading got easier — frameworks stream, CDNs are everywhere, images are finally responsive by default. Interaction latency is the new failure mode: hydration storms, third-party script pileups, and event handlers doing synchronous work they should defer.
- Break up long tasks: anything over 200ms of main-thread work gets chunked or moved off-thread
- Defer analytics and chat widgets until first interaction — nobody's tracking pixel is worth a red INP
- Hydrate islands, not oceans: partial hydration converted three of our worst INP offenders to green
- Measure with real devices: your M3 laptop lies to you about mid-range Android
The unglamorous winners
Font subsetting, image dimension attributes, and deleting dead JavaScript remain the highest ROI-per-hour fixes we do. On one retail client, removing four abandoned marketing scripts moved LCP by 800ms — no rebuild required.
Performance budgets in CI keep it green after we leave. A budget that fails the build is worth ten dashboards nobody reads.