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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
76
GRADE
C
FIX
3
REVIEW
2
PASS
7
INFO
2

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop
81
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
100
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
92
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

1.40 s

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

1.60 s

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

106 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.002

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

3.29 s

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

3.65 s

Page Load Progression

516 ms
1.0 s
1.5 s
2.1 s
2.6 s
3.1 s
3.6 s
4.1 s
Checks
14
7 PASS 2 REVIEW 3 FIX
F
Page Weight Budget
Action
3.5 MB transferred, 146 requests
FIX
3.5 MB transferred, 146 requests
Warning::
Page weighs 11.3 MB (3.5 MB transferred)
Warning::
Images are 2.3 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 2.3 MB
Warning::
JavaScript is 655 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 655 KB
Warning::
146 HTTP requests — consider bundling or reducing
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Info::
Estimated 0.74 g CO2 per page load
3.5 MB / 2.4 MB budget
3.5 MB transferred
146 requests
0.74 g CO2 per page load
Images 2.3 MiB 65%
JavaScript 655.1 KiB 18%
HTML 256.8 KiB 7%
Fonts 186.1 KiB 5%
CSS 155.4 KiB 4%
Other 16.3 KiB 0%
Other 7.5 KiB 0%
Other 1.8 KiB 0%
Other 1.3 KiB 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Over budget

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Why this matters

Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.

Source: web.dev

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Why this matters

JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.

Source: web.dev

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Why this matters

High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.

Source: web.dev

D
JS Bundles
Action
36 scripts, 354 KB unused
FIX
36 scripts, 354 KB unused
Warning::
https://www.lego.com/_next/static/chunks/pages/_ap...: 177 KB unused (46%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.lego.com/_next/static/chunks/pages/_ap...: 177 KB unused (46%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 354 KB
354 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.lego.com/_next/static/chunks/pages/_app-97dbd3923c220aee.js387 KB177 KB (46%)✓1st
https://www.lego.com/_next/static/chunks/pages/_app-97dbd3923c220aee.js0 KB177 KB (46%)✓1st
https://www.lego.com/_next/static/chunks/6954.4f6ece01da6247fb.js1 KB—✓1st
https://www.lego.com/_next/static/chunks/pages/%5Blocale%5D-abb08fe9efd697fd.js9 KB—✓1st
https://www.lego.com/_next/static/chunks/8534.2445c774ee407e2f.js4 KB—✓1st
https://www.lego.com/_next/static/chunks/85.e79aca66268170b0.js4 KB—✓1st
https://www.lego.com/_next/static/chunks/1044.8d310f6a026eb619.js1 KB—✓1st
https://www.lego.com/_next/static/chunks/6898.8b40048cd045d018.js4 KB—✓1st
https://www.lego.com/_next/static/chunks/2819.34265d36b448a72b.js4 KB—✓1st
https://www.lego.com/newrelic.js23 KB—✓1st

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

D
HTTP Caching
Action
no-store (uncacheable)
FIX
no-store (uncacheable)
Info::
Cache-Control: no-store prevents all caching
Intentional for dynamic content, but increases server load for every page view.
Got: private, max-age=0, no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

private, max-age=0, no-store, no-cache, must-revalidate, post-check=0, pre-check=0

DirectiveValueMeaning
private—Only browser cache, not CDN/proxy
max-age0Cache for 0 seconds
no-store—Never cache this response
no-cache—Cache but always revalidate first
must-revalidate—Must recheck with server after expiry
post-check0
pre-check0
C
Image Optimization
Action
62 images, 0 KB saveable
REVIEW
62 images, 0 KB saveable
Warning::
https://www.lego.com/cdn/cs/shopper-domain-terms/a... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/bltd117abf5... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blt456f4349... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blte9cb7be5... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/shopper-domain-terms/a... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/_next/static/images/play-zone... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blt60032fea... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/shopper-domain-terms/a... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blt7e2eca65... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/shopper-domain-terms/a... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/shopper-domain-terms/a... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/shopper-domain-terms/a... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/shopper-domain-terms/a... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blt379b25cd... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blt3e8dc492... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/shopper-domain-terms/a... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/bltbaf582bf... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blt43850a9b... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blt42e0983c... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.lego.com/cdn/cs/set/assets/blt32a94f40... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
62 images 2.3 MB
0 oversized -0 KB
61 legacy format
20 missing dimensions CLS risk

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

C
JS Execution Cost
Action
1704ms total JS execution
REVIEW
1704ms total JS execution
Warning::
https://www.lego.com/_next/static/chunks/framework...: 691ms CPU time
Warning::
https://www.lego.com/_next/static/chunks/pages/_ap...: 350ms CPU time
Warning::
Unattributable: 329ms CPU time
Info::
https://www.lego.com/en-es: 217ms CPU time
Info::
https://www.lego.com/newrelic.js: 65ms CPU time
Info::
Third-party scripts: 381ms (22% of total)

Main Thread Breakdown

Script Evaluation 57% Other 16% Style & Layout 13% Script Parsing & Compilation 7%
ScriptTotalScriptingParse/CompileParty
https://www.lego.com/_next/static/chunks/framework-743a406e6ea89f42.js691ms602ms9ms1st
https://www.lego.com/_next/static/chunks/pages/_app-97dbd3923c220aee.js350ms181ms85ms1st
Unattributable329ms68ms0ms3rd
https://www.lego.com/en-es217ms6ms0ms1st
https://www.lego.com/newrelic.js65ms54ms6ms1st
https://js-agent.newrelic.com/nr-spa-1.297.1.min.js51ms43ms4ms3rd
A+
Third-Party Impact
7% third-party, 0 ms blocking
PASS
7% third-party, 0 ms blocking
Info::
Third-party code accounts for 7% of page weight (246.3 KiB of 3.5 MiB)
Info::
Third-party blocking time is low (0 ms)
93%
First-party Third-party
A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
Font Loading
8 fonts (186 KB)
PASS
8 fonts (186 KB)
Info::
8 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

8

186 KB total

Render-blocking

0

of 8

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s 1.5 s FCP 1.4 s LCP 1.6 shttps://assets.lego.com/fonts/v3/cera-pro/CeraPro-Regular.woff2CeraPro-Regular.woff2 https://assets.lego.com/fonts/v3/cera-pro/CeraPro-Regular.woff2 — 46.2 KiB — 0 ms — font-display: swaphttps://assets.lego.com/fonts/v3/cera-pro/CeraPro-Medium.woff2CeraPro-Medium.woff2 https://assets.lego.com/fonts/v3/cera-pro/CeraPro-Medium.woff2 — 46.1 KiB — 0 ms — font-display: swaphttps://assets.lego.com/fonts/v3/cera-pro/CeraPro-RegularItalic.woff2CeraPro-RegularItalic.w... https://assets.lego.com/fonts/v3/cera-pro/CeraPro-RegularItalic.woff2 — 48.1 KiB — 0 ms — font-display: swaphttps://assets.lego.com/fonts/v3/cera-pro/CeraPro-Bold.woff2CeraPro-Bold.woff2 https://assets.lego.com/fonts/v3/cera-pro/CeraPro-Bold.woff2 — 45.7 KiB — 0 ms — font-display: swaphttps://assets.lego.com/fonts/v3/cera-pro/CeraPro-RegularItalic.woff2CeraPro-RegularItalic.w... https://assets.lego.com/fonts/v3/cera-pro/CeraPro-RegularItalic.woff2 — 0 B — 0 ms — font-display: swaphttps://assets.lego.com/fonts/v3/cera-pro/CeraPro-Medium.woff2CeraPro-Medium.woff2 https://assets.lego.com/fonts/v3/cera-pro/CeraPro-Medium.woff2 — 0 B — 0 ms — font-display: swaphttps://assets.lego.com/fonts/v3/cera-pro/CeraPro-Bold.woff2CeraPro-Bold.woff2 https://assets.lego.com/fonts/v3/cera-pro/CeraPro-Bold.woff2 — 0 B — 0 ms — font-display: swaphttps://assets.lego.com/fonts/v3/cera-pro/CeraPro-Regular.woff2CeraPro-Regular.woff2 https://assets.lego.com/fonts/v3/cera-pro/CeraPro-Regular.woff2 — 0 B — 0 ms — font-display: swap
CeraPro-Regular.woff2 woff2 swap
Size 46 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
CeraPro-Medium.woff2 woff2 swap
Size 46 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
CeraPro-RegularItalic.w... woff2 swap
Size 48 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
CeraPro-Bold.woff2 woff2 swap
Size 46 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
CeraPro-RegularItalic.w... woff2 swap
Size 0 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
CeraPro-Medium.woff2 woff2 swap
Size 0 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
CeraPro-Bold.woff2 woff2 swap
Size 0 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
CeraPro-Regular.woff2 woff2 swap
Size 0 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Optimization checklist
  • Preload critical fonts (priority=high)
  • Use woff2 format for all fonts
  • Set font-display to swap, optional, or fallback
  • Subset large fonts (≤100 KB each)
A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

Network Waterfall
146 requests over 0ms
INFO

Performance analysis not available for this result.

Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
22% of JavaScript execution is third-party
First-party Third-party 381ms · 0KB · $5/mo
Unattributable
Other
Costly
Execution 329ms
Transfer 0 KB
Monthly Cost $4/mo
js-agent.newrelic.com
Other
Optional
Execution 51ms
Transfer 0 KB
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • Unattributable adds 329ms and costs ~$4/month

Unattributable takes 329ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

How third-party costs are calculated

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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