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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
78
GRADE
C
FIX
2
REVIEW
3
PASS
7
INFO
2

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

Mobile Desktop
78
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
95
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
77
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.

621 ms

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

4.35 s

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

0 ms

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

0.008

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

924 ms

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

4.35 s

Page Load Progression

388 ms
775 ms
1.2 s
1.6 s
1.9 s
2.3 s
2.7 s
3.1 s
Checks
14
7 PASS 3 REVIEW 2 FIX
F
Page Weight Budget
Action
3.8 MB transferred, 62 requests
FIX
3.8 MB transferred, 62 requests
Warning::
Page weighs 5.5 MB (3.8 MB transferred)
Info::
Fonts are 3.0 MB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 3.0 MB
Warning::
JavaScript is 641 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 641 KB
Info::
62 HTTP requests
Info::
Estimated 0.79 g CO2 per page load
3.8 MB / 2.4 MB budget
3.8 MB transferred
62 requests
0.79 g CO2 per page load
Fonts 3.0 MiB 80%
JavaScript 640.9 KiB 17%
Images 59.2 KiB 2%
HTML 37.8 KiB 1%
Other 15.8 KiB 0%
CSS 12.9 KiB 0%
Other 1.4 KiB 0%
Other 973 B 0%
0 2.4 MB 4.9 MB
Over budget

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

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

D
JS Bundles
Action
26 scripts, 317 KB unused
FIX
26 scripts, 317 KB unused
Warning::
https://codesandbox.io/_next/static/chunks/9230-85...: 85 KB unused (96%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://codesandbox.io/_next/static/chunks/9331-ab...: 69 KB unused (55%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://codesandbox.io/_next/static/chunks/ec0da94...: 45 KB unused (90%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://codesandbox.io/_next/static/chunks/2409-a2...: 36 KB unused (73%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://codesandbox.io/_next/static/chunks/ef9c525...: 34 KB unused (77%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 317 KB
317 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://codesandbox.io/_next/static/chunks/9230-85da48510973f4ae.js89 KB85 KB (96%)✓1st
https://codesandbox.io/_next/static/chunks/9331-ab608ee9ae01eddb.js126 KB69 KB (55%)✓1st
https://codesandbox.io/_next/static/chunks/ec0da940-7fe13e19c1ef37bc.js51 KB45 KB (90%)✓1st
https://codesandbox.io/_next/static/chunks/2409-a2745fd5e5a7ed70.js50 KB36 KB (73%)✓1st
https://codesandbox.io/_next/static/chunks/ef9c525d-794586603a2cf360.js45 KB34 KB (77%)✓1st
https://codesandbox.io/_next/static/chunks/3037-34ebfe82f03e16ac.js33 KB24 KB (75%)✓1st
https://codesandbox.io/_next/static/chunks/e332d428-607a0fc2b0f712b1.js34 KB22 KB (67%)✓1st
https://codesandbox.io/_next/static/chunks/9348-4ca373a6936773be.js3 KB—✓1st
https://codesandbox.io/_next/static/chunks/1261-d0847cd35a4e9b63.js10 KB—✓1st
https://codesandbox.io/_next/static/chunks/f923c8e2-e4529f531e4e04c4.js1 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

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

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

B
Image Optimization
22 images, 0 KB saveable
REVIEW
22 images, 0 KB saveable
Info::
All images are well-optimized
22 images 59 KB
0 oversized -0 KB
8 legacy format
0 missing dimensions CLS risk
B
JS Execution Cost
922ms total JS execution
REVIEW
922ms total JS execution
Warning::
https://codesandbox.io/: 493ms CPU time
Info::
https://codesandbox.io/_next/static/chunks/7157-f1...: 172ms CPU time
Info::
https://codesandbox.io/_next/static/chunks/3a1fbd1...: 95ms CPU time
Info::
https://codesandbox.io/cdn-cgi/challenge-platform/...: 87ms CPU time
Info::
Unattributable: 77ms CPU time
Info::
Third-party scripts: 77ms (8% of total)

Main Thread Breakdown

Other 31% Script Evaluation 30% Style & Layout 21% Rendering 10% Script Parsing & Compilation 5%
ScriptTotalScriptingParse/CompileParty
https://codesandbox.io/493ms11ms5ms1st
https://codesandbox.io/_next/static/chunks/7157-f1dd02184197292d.js172ms143ms3ms1st
https://codesandbox.io/_next/static/chunks/3a1fbd1c-9a309fde5120dbc5.js95ms17ms5ms1st
https://codesandbox.io/cdn-cgi/challenge-platform/scripts/jsd/main.js87ms71ms1ms1st
Unattributable77ms2ms0ms3rd
B
HTTP Caching
s-maxage=31536000, stale-while-revalidate
REVIEW
s-maxage=31536000, stale-while-revalidate
Info::
Cache-Control header is set
Got: s-maxage=31536000, stale-while-revalidate
Info::
CDN TTL: 52 weeks (s-maxage=31536000)
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

s-maxage=31536000, stale-while-revalidate

DirectiveValueMeaning
s-maxage31536000CDN caches for 52 weeks
stale-while-revalidate—Serve stale while revalidating
A+
Third-Party Impact
2% third-party, 0 ms blocking
PASS
2% third-party, 0 ms blocking
Info::
Third-party code accounts for 2% of page weight (58.8 KiB of 3.8 MiB)
Info::
Third-party blocking time is low (0 ms)
98%
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
3 fonts (3089 KB)
PASS
3 fonts (3089 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

3089 KB total

Render-blocking

0

of 3

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 1.0 s 2.0 s 3.0 s 4.0 s FCP 621 ms LCP 4.4 shttps://codesandbox.io/_next/static/media/e4af272ccee01ff0-s.p.woff2e4af272ccee01ff0-s.p.woff2 https://codesandbox.io/_next/static/media/e4af272ccee01ff0-s.p.woff2 — 47.5 KiB — 0 ms — font-display: swaphttps://codesandbox.io/_next/static/media/material-symbols-outlined.43ee5b2a.woff2material-symbols-outlin... https://codesandbox.io/_next/static/media/material-symbols-outlined.43ee5b2a.woff2 — 2.9 MiB — 0 ms — font-display: swaphttps://codesandbox.io/new/fonts/TWKEverett-Medium-web.woff2TWKEverett-Medium-web.w... https://codesandbox.io/new/fonts/TWKEverett-Medium-web.woff2 — 59.9 KiB — 0 ms — font-display: swap
e4af272ccee01ff0-s.p.woff2 woff2 swap
Size 48 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
material-symbols-outlin... woff2 swap
Size 2982 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
TWKEverett-Medium-web.w... woff2 swap
Size 60 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)

Fixing the unchecked items could save ~1491 KB and ~2982 ms

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
62 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
8% of JavaScript execution is third-party
First-party Third-party 77ms · 0KB · kr141/mo
Unattributable
Other
Costly
Execution 77ms
Transfer 0 KB
Monthly Cost kr141/mo

These scripts may cost more than they're worth

  • Unattributable adds 77ms and costs ~kr141/month

Unattributable takes 77ms 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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