Find what's slowing your site. Fix it in hours.

Joltsite shows you the exact scripts, DOM elements, and pages dragging your Core Web Vitals down. Stop guessing why your LCP is slow — see the specific third-party script or image causing it.

Start monitoring now See how it works

Plans from €9.99/mo — every feature included on every plan

Perfbear dashboard showing Core Web Vitals overview with LCP, INP, CLS scores and rating distribution

You know your Core Web Vitals need work.
But where do you start?

PageSpeed Insights tells you your LCP is 4.2s. Great. But it doesn't tell you which script is blocking render, which image loads too late, or which element shifts on mobile. You end up spending weeks A/B testing guesses instead of fixing the actual problem.

53%

of visits abandoned if a mobile page takes over 3s to load

~60%

of websites lack enough traffic for CrUX field data

Hours

to identify and fix your worst bottleneck with the right data

From "my site is slow" to "here's exactly why"

Joltsite connects to your GA4 BigQuery export or collects field data via a lightweight RUM snippet. Either way, you get page-level, element-level debugging in minutes.

Connect your data

Point Joltsite at your GA4 BigQuery dataset, or drop our 2KB RUM script onto your site. No sampling, no aggregation — real metrics from real visitors on every page load.

See what's broken

Drill into per-page metrics. See which DOM element is your LCP target, which element triggered a layout shift, which interaction had the worst INP. Filter by device, percentile (P75/P90/P95/P99), and time range.

Fix and verify

Use the script analysis to find third-party JavaScript correlated with poor scores. Remove or defer the offending script, deploy, and watch your metrics turn green in the time-series chart.

Script impact analysis showing load times, transfer sizes, and correlation with poor Core Web Vitals

Script analysis shows exactly which JavaScript is dragging your vitals down

Built for debugging, not just dashboards

Most monitoring tools give you a score and leave you to figure out the rest. Joltsite traces each poor metric back to a specific element or script.

Script impact analysis

See every JavaScript resource loaded on your site with median and P75 load time, transfer size, and render-blocking status. Each script gets a correlation score showing its impact on poor LCP, INP, and FCP — so you know exactly which third-party script to defer or remove.

Debug elements

For LCP, CLS, and INP, Joltsite identifies the actual DOM element responsible. Not "reduce layout shifts" — but "div.hero-banner shifted 47 times on mobile with a P75 of 0.18". Each element shows occurrence count, percentile values, and rating distribution.

Page-level drill-downs

Break down metrics per page to find the worst offenders. Your homepage might pass all Core Web Vitals while /checkout has a 6s LCP on mobile. Create URL groups with pattern matching (e.g. /products/*) to track aggregate performance across any route set.

Slice by device and percentile

Filter all data by desktop, phone, or tablet. Switch between P75, P90, P95, and P99 to understand how your worst-performing visitors experience your site. A passing P75 can hide serious issues at P95 on mobile — Joltsite makes that gap visible instantly.

Trend monitoring

Time-series charts show how each metric changes over 7, 28, or 90 days. Color-coded data points (green/amber/red) show the rating at each date. Overlay multiple metrics to spot when a deploy regressed INP while improving LCP. Bookmark critical pages for your daily performance check.

MCP server for AI agents

Connect Joltsite to Claude, Cursor, or any MCP-compatible AI tool. Your AI coding agent can query vitals, list slow pages, inspect debug targets, and suggest fixes — all from your editor. Generate an API token and point your MCP client at our server.

Performance over time chart showing Core Web Vitals trends across 28 days with color-coded rating points

Track how your vitals change over time — spot regressions the day they happen

Two ways to collect field data

Use the data source that fits your stack. Both give you the same debugging power.

GA4 BigQuery export

Already streaming GA4 events to BigQuery? Connect your dataset and Joltsite reads web vitals directly — no extra script on your pages.

Zero additional page weight
Uses data you already collect
Per-website or shared service account credentials

Lightweight RUM script

Drop a tiny JavaScript snippet onto your site. Collects LCP, CLS, INP, FCP, TTFB, resource timing, and debug targets — nothing else.

Under 2KB gzipped
No cookies, no PII — GDPR-friendly by design
Script + resource timing included

Pricing that doesn't punish small sites

Every plan includes every feature. No paywalled metrics, no "upgrade to see debug data". You only pay for volume.

StarterBlogs & side projects

Everything you need for a personal site or small project

€9.99/mo

50K pageviews/mo
2 websites
Script impact analysis
Debug elements (LCP, CLS, INP)
URL groups & page drill-downs
MCP server access

Start for €9.99

Your next deploy could fix your worst metric

Most performance work stalls because teams can't pinpoint the cause. Joltsite shows you the exact script, element, or page to fix — so your next deploy actually moves the needle.

Start monitoring now

Plans from €9.99/mo — every feature included