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Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
79
GRADE
C
FIX
4
REVIEW
1
PASS
9
INFO
2

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

Mobile Desktop
40
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
89
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.
100
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.

6.31 s

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

6.94 s

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

916 ms

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

0.001

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

6.31 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.

11.51 s

Page Load Progression

375 ms
750 ms
1.1 s
1.5 s
1.9 s
2.2 s
2.6 s
3.0 s
Checks
16
9 PASS 1 REVIEW 4 FIX
D
Third-Party Impact
Action
98% third-party, 0 ms blocking
FIX
98% third-party, 0 ms blocking
Warning::
Third-party code accounts for 98% of page weight (1.2 MiB of 1.3 MiB)
Info::
Third-party blocking time is low (0 ms)
98%
First-party Third-party
F
JS Execution Cost
Action
4280ms total JS execution
FIX
4280ms total JS execution
Warning::
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_...: 1664ms CPU time
Warning::
Unattributable: 1022ms CPU time
Warning::
https://m.youtube.com/: 558ms CPU time
Warning::
https://m.youtube.com/s/player/57fefa84/player-pla...: 259ms CPU time
Info::
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_...: 178ms CPU time
Warning::
Third-party scripts: 4280ms (100% of total)

Main Thread Breakdown

Script Evaluation 62% Other 20% Script Parsing & Compilation 9% Parse HTML & CSS 4%
ScriptTotalScriptingParse/CompileParty
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=root,c3_base,zcskIc,SFvGjc,cDTHu,JoU6vf,Di4hBc,dpUCFd,Nuilue1664ms1358ms178ms3rd
Unattributable1022ms204ms0ms3rd
https://m.youtube.com/558ms162ms63ms3rd
https://m.youtube.com/s/player/57fefa84/player-plasma-es6-en_US.vflset/base.js259ms102ms153ms3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/exm=Cj1YCb,Di4hBc,JoU6vf,Nuilue,OtKSJe,Rv3e3d,SFvGjc,c3_base,cDTHu,dpUCFd,hBod9c,hjrNn,jVxNAb,qiuJmb,root,tkEWoe,zcskIc/ed=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=ERsVff178ms114ms43ms3rd
https://m.youtube.com/static/r/84ceb080/scheduler.vflset/scheduler.js168ms133ms3ms3rd
https://www.google.com/js/th/PF32M1WFt3Opj6X4HHxBvSVo4hj3YoJbcs9XKKWIAD0.js114ms106ms7ms3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/exm=Di4hBc,JoU6vf,Nuilue,SFvGjc,c3_base,cDTHu,dpUCFd,root,zcskIc/ed=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=Rv3e3d97ms87ms8ms3rd
https://m.youtube.com/s/player/57fefa84/mobile-polymer-player-svg-ias-mweb.css95ms0ms0ms3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/exm=Cj1YCb,Di4hBc,ERsVff,JoU6vf,Nuilue,OtKSJe,Rv3e3d,SFvGjc,c3_base,cDTHu,dpUCFd,hBod9c,hjrNn,jVxNAb,qiuJmb,root,tkEWoe,zcskIc/ed=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=dfXAxf67ms57ms1ms3rd

Showing top 10 of 11 scripts

F
JS Bundles
Action
12 scripts, 598 KB unused
FIX
12 scripts, 598 KB unused
Warning::
https://m.youtube.com/s/player/57fefa84/player-pla...: 307 KB unused (74%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_...: 232 KB unused (54%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_...: 59 KB unused (77%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 598 KB
598 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://m.youtube.com/s/player/57fefa84/player-plasma-es6-en_US.vflset/base.js416 KB307 KB (74%)✓3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=root,c3_base,zcskIc,SFvGjc,cDTHu,JoU6vf,Di4hBc,dpUCFd,Nuilue434 KB232 KB (54%)✓3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/exm=Cj1YCb,Di4hBc,JoU6vf,Nuilue,OtKSJe,Rv3e3d,SFvGjc,c3_base,cDTHu,dpUCFd,hBod9c,hjrNn,jVxNAb,qiuJmb,root,tkEWoe,zcskIc/ed=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=ERsVff77 KB59 KB (77%)✓3rd
https://m.youtube.com/static/r/84ceb080/scheduler.vflset/scheduler.js3 KB—✓3rd
https://m.youtube.com/static/r/84ceb080/fetch_polyfill.vflset/fetch_polyfill.js3 KB—✓3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/exm=Di4hBc,JoU6vf,Nuilue,SFvGjc,c3_base,cDTHu,dpUCFd,root,zcskIc/ed=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=Rv3e3d17 KB—✓3rd
https://www.google.com/js/th/PF32M1WFt3Opj6X4HHxBvSVo4hj3YoJbcs9XKKWIAD0.js23 KB—✓3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/exm=Di4hBc,JoU6vf,Nuilue,Rv3e3d,SFvGjc,c3_base,cDTHu,dpUCFd,root,zcskIc/ed=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=hBod9c0 KB—✓3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/exm=Di4hBc,JoU6vf,Nuilue,Rv3e3d,SFvGjc,c3_base,cDTHu,dpUCFd,hBod9c,root,zcskIc/ed=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=OtKSJe1 KB—✓3rd
https://m.youtube.com/s/_/ytmweb/_/js/k=ytmweb.c3_base.en_US.H8Ls_CPT03Y.2021.O/am=AAAAAAM/d=1/exm=Di4hBc,JoU6vf,Nuilue,OtKSJe,Rv3e3d,SFvGjc,c3_base,cDTHu,dpUCFd,hBod9c,root,zcskIc/ed=1/br=1/rs=ABnK5FJkT080TkAAQpuU1E0_YRT_YGgJ1g/m=qiuJmb,hjrNn,tkEWoe,Cj1YCb,jVxNAb2 KB—✓3rd

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

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: no-cache, no-store, max-age=0, must-revalidate
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

no-cache, no-store, max-age=0, must-revalidate

DirectiveValueMeaning
no-cache—Cache but always revalidate first
no-store—Never cache this response
max-age0Cache for 0 seconds
must-revalidate—Must recheck with server after expiry
B
Page Weight Budget
1.3 MB transferred, 73 requests
REVIEW
1.3 MB transferred, 73 requests
Info::
Page weighs 5.2 MB (1.3 MB transferred)
Warning::
JavaScript is 978 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 978 KB
Info::
73 HTTP requests
Info::
Estimated 0.27 g CO2 per page load
1.3 MB / 2.4 MB budget
1.3 MB transferred
73 requests
0.27 g CO2 per page load
JavaScript 977.8 KiB 75%
CSS 183.0 KiB 14%
HTML 59.9 KiB 5%
Fonts 28.1 KiB 2%
Other 26.3 KiB 2%
Other 13.5 KiB 1%
Other 5.1 KiB 0%
Images 1.2 KiB 0%
Other 341 B 0%
0 2.4 MB 4.9 MB
Under budget

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

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
Image Optimization
3 images, 0 KB saveable
PASS
3 images, 0 KB saveable
Info::
All images are well-optimized
3 images 1 KB
0 oversized -0 KB
2 legacy format
0 missing dimensions CLS risk
A+
Font Loading
2 fonts (28 KB)
PASS
2 fonts (28 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

28 KB total

Render-blocking

0

of 2

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 5.0 s 6.0 s 7.0 s FCP 6.3 s LCP 6.9 shttps://fonts.gstatic.com/s/roboto/v18/KFOmCnqEu92Fr1Mu4mxPKTU1Kg.ttfKFOmCnqEu92Fr1Mu4mxPKTU... https://fonts.gstatic.com/s/roboto/v18/KFOmCnqEu92Fr1Mu4mxPKTU1Kg.ttf — 14.0 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/roboto/v18/KFOlCnqEu92Fr1MmEU9fBBc9AMP6lQ.ttfKFOlCnqEu92Fr1MmEU9fBBc... https://fonts.gstatic.com/s/roboto/v18/KFOlCnqEu92Fr1MmEU9fBBc9AMP6lQ.ttf — 14.1 KiB — 0 ms — font-display: swap
KFOmCnqEu92Fr1Mu4mxPKTU... ttf swap
Size 14 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
KFOlCnqEu92Fr1MmEU9fBBc... ttf swap
Size 14 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
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 ~8 KB and ~16 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+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
No render-blocking resources detected in <head>
A+
Third-Party Resources
No third-party resources detected
PASS
No third-party resources detected
A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Google Cloud

Network Waterfall
73 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
100% of JavaScript execution is third-party
First-party Third-party 4280ms · 1093KB · $57/mo
m.youtube.com
Other
Costly
Execution 1664ms
Transfer 434 KB
Unused 54%
Monthly Cost $22/mo
Unattributable
Other
Costly
Execution 1022ms
Transfer 0 KB
Monthly Cost $14/mo
m.youtube.com
Other
Costly
Execution 558ms
Transfer 59 KB
Monthly Cost $7/mo
m.youtube.com
Other
Costly
Execution 259ms
Transfer 416 KB
Unused 74%
Monthly Cost $3/mo
m.youtube.com
Other
Optional
Execution 178ms
Transfer 77 KB
Unused 77%
Monthly Cost $2/mo
m.youtube.com
Other
Optional
Execution 168ms
Transfer 3 KB
Monthly Cost $2/mo
www.google.com
Other
Optional
Execution 114ms
Transfer 23 KB
Monthly Cost $2/mo
m.youtube.com
Other
Optional
Execution 97ms
Transfer 17 KB
Monthly Cost $1/mo
m.youtube.com
Other
Optional
Execution 95ms
Transfer 60 KB
Monthly Cost $1/mo
m.youtube.com
Other
Optional
Execution 67ms
Transfer 1 KB
Monthly Cost $1/mo
m.youtube.com
Other
Optional
Execution 59ms
Transfer 2 KB
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • m.youtube.com adds 1664ms and costs ~$22/month
  • Unattributable adds 1022ms and costs ~$14/month
  • m.youtube.com adds 558ms and costs ~$7/month
  • m.youtube.com adds 259ms and costs ~$3/month

100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.

Why this matters

When third-party JS execution time exceeds your own, performance gains from frontend work are capped by code you don't own.

Learn more ▾

Every millisecond of third-party JS competes with your own for main-thread time. If their share is bigger than yours, optimization on your code base barely moves the needle. Audit, defer, or remove third-parties before further frontend optimization. Use Lighthouse's third-party audit to identify the worst offenders.

Source: web.dev

m.youtube.com takes 1664ms 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

54% of m.youtube.com's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

Unattributable takes 1022ms 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

m.youtube.com takes 558ms 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

m.youtube.com takes 259ms 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

74% of m.youtube.com's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

77% of m.youtube.com's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

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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