Next.js Core Web Vitals
Field-data LCP, CLS, and INP tracking with regression alerts.
The Next.js-specific angle
Next.js apps regress on INP first — heavy client components hydrated on scroll block the main thread long after LCP has already painted. Vercel Analytics reports p75 but hides the interaction that caused it; that's the gap we close.
What we watch on Next.js
- INP spikes after a deploy that adds a new client component to a shared layout
- LCP regression when next/image switches to unoptimised mode under load
- CLS from Google Fonts loaded via next/font/google without size-adjust
Universal core web vitals checks
Same on every stack — these run on your Next.js site out of the box:
- Largest Contentful Paint (LCP) — 75th percentile, tracked hourly
- Cumulative Layout Shift (CLS) — with the specific shifting element flagged
- Interaction to Next Paint (INP) — replaces FID for 2026 rankings
- Alerts fire when the 7-day rolling baseline degrades by >20%
Reference thresholds we alert against
How Lemwatch handles it on Next.js
We pull field data every hour and correlate regressions with your deploy events, so an INP jump maps back to a specific commit — not a vague 'performance is worse this week'.
More Next.js monitoring guides
Core Web Vitals on other stacks
Next.js Core Web Vitals — FAQs
We pull field data every hour and correlate regressions with your deploy events, so an INP jump maps back to a specific commit — not a vague 'performance is worse this week'.
Next.js apps regress on INP first — heavy client components hydrated on scroll block the main thread long after LCP has already painted. Vercel Analytics reports p75 but hides the interaction that caused it; that's the gap we close.
No. Lemwatch is fully black-box — we monitor what visitors and Googlebot see. Add your domain, checks start within 60 seconds, and no plugin, SDK, or code change is required in your Next.js app.
Pro plans run 1-minute checks from multiple regions. When a regression trips a rule (e.g. p75 LCP up >20% for 3 consecutive windows, or cert expiry <7 days), the notification fires within the next check cycle — typically 60 seconds.
Yes. Add HTTP basic auth headers or a bearer token per site, and Lemwatch treats staging as an isolated site — flaky preview envs won't pollute your production status board.