Always-on monitoring of Cumulative Layout Shift. Sentry catches sized-image regressions, font-swap shifts, late-loading ads, and dynamic content pushing the page around before users hit the 0.1 p75 cliff. Cortex handles the fix.
Continuous audits of mobile + desktop CLS against Google's 0.1 threshold and the documented diagnostics that explain every shifted pixel. Each rule maps to a primary web.dev CLS doc. Sentry catches what fails. Cortex fixes it.
CrUX 28-day p75 CLS on phone form factor under Google's 0.1 'Good' threshold. Mobile field CLS is the metric Google uses for the mobile Page Experience signal.
CrUX 28-day p75 CLS on desktop under Google's 0.1 'Good' threshold. Desktop field CLS is the metric Google uses for the desktop Page Experience signal.
Lighthouse mobile-emulated CLS from PSI under 0.1. Lab CLS captures shifts during initial page load (Lighthouse can't simulate user-driven shifts) and surfaces regressions before field data updates.
Lighthouse layout-shift-elements audit reports zero shifting elements during load. Every element listed is one that moved during the page lifecycle - usually a sized-image, web-font, or late-injected ad/banner.
Lighthouse unsized-images audit passes - every `<img>` carries width + height attributes (or aspect-ratio CSS). Unsized images force a reflow as soon as the image arrives, which is the #1 CLS contributor on most sites.
Every @font-face declares font-display: swap, fallback, or optional. Default font-display behavior (block) hides text until the font loads, then swaps - producing a font-related layout shift on every paint.
A `<meta name='viewport' content='width=device-width'>` tag in the head. Missing viewport meta defaults mobile browsers to a 980px desktop viewport, then snaps to mobile width on load - a CLS-amplifying reflow.
No `<iframe>` in the above-the-fold HTML lacks a fixed height (style or attribute). Ad iframes that load late and then resize push every below-them element down, inflating CLS.
Paste your homepage URL. Sentry runs PSI for mobile + desktop, pulls 28-day CrUX field CLS, and inspects Lighthouse's layout-shift-elements, unsized-images, font-display, viewport meta, and dynamic-iframe diagnostics. No signup, instant results, always free.
Sentry fetches your site, runs every CLS rule, and renders the full result page before your next sip of coffee.
Each failed rule ships with a prescription paragraph. Hand it to engineering and the gap is closed before lunch.
Add your site to the daily Sentry sweep with one click. New regressions get caught the next morning.
8 rules in the CLS Sentry. Daily 3:30 AM ET sweep.
One brain. Thirty-six pairs of eyes. Sentries monitor every visibility signal that decides whether search engines, AI engines, and ad platforms show you. Cortex reads what they see, weighs it against a unified corpus of platform documentation, and acts. Every move follows a defined decision protocol: action stated, reason given, impact named.