Find the cause of a slow site,
not just a low score.

Check whether the server, JavaScript, CSS, images, fonts or third-party scripts slow the page down. Get a fix order and compare the score after shipping.

Illustrative product view
82
CometWeb module score 82/100 · example · Insight scale How we calculate the score →
LCP · Lab
2.8s
CLS · Lab
0.12
TBT · Lab
420ms
Insight combines the Lighthouse score, CrUX data, waterfall and asset analysis.

Then it groups issues, estimates impact and orders the fixes — instead of leaving you with a score alone.

  • Data source

    Lab, CrUX or no measurement — never faked.

  • User impact

    The metric, asset or request that actually costs time.

  • Recommended next step

    A fix priority and a retest after shipping.

From score to a fix plan.

Four steps from test to decision — without guessing where to start.

Core Web Vitals Scan

LCP, INP, CLS — lab data and field data when available.

LCPINPCLS
JavaScript

Heavy scripts, long tasks and interaction impact.

BundleTBT
Page assets

Images, fonts, CSS and third-party network requests.

MediaFonts

Page analysis

Measure key metrics, server and assets for a specific URL.

Core Web Vitals · lab
LCP 2.8 s
Needs work
INP 180 ms
Borderline
CLS 0.12
Passing
Lab · CrUX when available

Explain the causes

Connect a weak score to an element, request or code fragment.

Performance priorities
9

Fix priorities

Start with changes that have the highest impact and a sensible cost.

91
+9
82 before
91 after

Verify the effect after shipping

Compare before and after under the same measurement conditions.

What the module checks

  • Core Web Vitals
  • JavaScript
  • CSS
  • Server & TTFB
  • Images & fonts
  • Waterfall
  • Experience

Metrics and context

The overall score is a starting point, not the goal.

The goal is improving a specific user metric without making other areas worse. The module separates field data (CrUX), lab measurement (Lighthouse / Playwright) and Insight’s synthetic score — and when data is missing, it shows why instead of a zero.

  • Field data: LCP, INP, CLS · 28 days
  • Lab: LCP, CLS, TBT, Speed Index
  • Missing data = N/A with a reason
Lab · Today · desktop
LCP
0.4 s
lab · threshold ≤ 2.5s
TBT
120 ms
lab · instead of INP
CLS
0.002
lab · threshold ≤ 0.1
Rendering filmstrip (lab) LCP @ 0.4 s
LCP
0.0s0.1s0.2s0.4s0.6s0.8s1.0s1.5s

Code and assets

See which assets cost the most time and transfer.

JavaScript, CSS and media are the most common sources of delay. The module shows which scripts block the main thread, which styles delay rendering and which files can be deferred or optimized.

  • Heavy scripts and long tasks
  • Render-blocking CSS
  • Images, fonts and third-party assets
Asset map
transfer · gzip / compressed
1012 KB
Media hero.avif LCP

Largest payload · srcset / WebP

412 KB · 41% transfer share

Load process

See request order and what delays rendering.

The waterfall shows DNS, connection/TLS, TTFB, download, main-thread blocking and render-blocking resources. The filmstrip shows what visitors actually see — not just test numbers.

  • DNS · TLS · TTFB · download
  • Main-thread blocking
  • Render-blocking resources
Timeline · navigation → load 0 → 900 ms
FCP/LCP 401
load 818
0150300450600750900 ms
Critical chain: 2 levels 62 req · 4 phases
Request
0150300450600750900 ms
FCP/LCP 401
Size

Mobile and history

Different device. Different result. Same URL.

You compare profiles within the same run or historical measurements of the same URL and page version. A weaker CPU and slower connection often reveal issues invisible on desktop.

  • Mobile · 4G and Desktop · broadband
  • Same URL and page version
  • Run history and regressions
cometweb.io/
Same URL and page version
Mobile · 4G · Jun 14
LCP 2.8 s
TBT 420 ms
CLS 0.05
Measurement history same URL · last 30 days
Module walkthrough example

From a heavy hero to a faster LCP.

A demonstrative scenario — not an anonymized client case.

Problem A 1.4 MB hero image delayed LCP
Priority AVIF + preload the right variant
Before LCP 3.8 s
After LCP 2.2 s

Lighthouse mobile · same profile

For agencies and freelancers

Built for working across many client sites.

  • Switch domains and specific client subpages
  • Compare historical runs before/after
  • Export metrics and refresh a selected module

Find the first bottleneck.

Analyze a specific URL, find what slows loading and start with the highest-impact fix.

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