Always-on lab monitoring of Speed Index - Lighthouse's score for how quickly above-the-fold pixels populate frame by frame. Speed Index catches render-path regressions that LCP and FCP miss because it measures the entire fold, not a single element. Cortex handles the fix.
Continuous lab audits of Speed Index against Lighthouse's 3.4s 'Good' threshold and the documented diagnostics that explain why frames stall. Speed Index sees what FCP and LCP miss - the entire above-the-fold paint timeline, not a single element. Sentry catches what fails. Cortex fixes it.
Lighthouse mobile-emulated Speed Index under 3.4s. Speed Index computes the weighted-average time at which visible pixels above the fold settled - a slow score means individual elements rendered late even if FCP and LCP individually passed.
Lighthouse desktop-emulated Speed Index under 3.4s. Desktop scores typically fall under 1.5s; anything past 3.4s indicates render-blocking or animation issues that even fast connections can't recover.
First Contentful Paint under 1.8s on mobile. Speed Index can't start its pixel-progress measurement until FCP fires - a slow FCP guarantees a slow Speed Index regardless of how the rest of the page renders.
Zero synchronous `<script>` or unscoped `<link rel='stylesheet'>` in the head blocking the visual progress timeline. Render-blocking resources defer the entire frame sequence Speed Index measures.
Every @font-face declares font-display: swap, fallback, or optional. Default font-display (block) leaves the text frame blank for up to 3 seconds - which Speed Index counts against the score even when no text appears.
Paste your homepage URL. Sentry runs PSI for mobile + desktop, pulls Lighthouse lab Speed Index + FCP + render-blocking + font-display audits, and ships a per-rule report. No signup, instant results, always free.
Sentry fetches your site, runs every SPEED INDEX 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.
5 rules in the SPEED INDEX 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.