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https://www.booking.com

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
65
GRADE
D
FIX
5
REVIEW
2
PASS
5
INFO
2

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

Mobile Desktop
4
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
96
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.
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.

7.28 s

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

24.86 s

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

9.95 s

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

0.583

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

10.28 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.

33.53 s

Page Load Progression

715 ms
1.4 s
2.1 s
2.9 s
3.6 s
4.3 s
5.0 s
5.7 s
Checks
14
5 PASS 2 REVIEW 5 FIX
F
Page Weight Budget
Action
5.2 MB transferred, 304 requests
FIX
5.2 MB transferred, 304 requests
Critical::
Page weighs 16.9 MB (5.2 MB transferred)
Warning::
JavaScript is 3.9 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 3.9 MB
Info::
CSS is 206 KB — consider purging unused styles
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
Got: 206 KB
Warning::
304 HTTP requests — consider bundling or reducing
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Info::
Estimated 1.1 g CO2 per page load
5.2 MB / 2.4 MB budget
5.2 MB transferred
304 requests
1.1 g CO2 per page load
JavaScript 3.9 MiB 74%
Images 641.1 KiB 12%
CSS 205.7 KiB 4%
Other 168.5 KiB 3%
HTML 167.4 KiB 3%
Other 121.9 KiB 2%
Other 51.5 KiB 1%
Fonts 41.6 KiB 1%
Other 1.5 KiB 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Over 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

Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.

Why this matters

CSS bundle is large — purge unused styles (PurgeCSS, Tailwind JIT) to reduce CSS payload.

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
Third-Party Impact
Action
86% third-party, 0 ms blocking
FIX
86% third-party, 0 ms blocking
Warning::
Third-party code accounts for 86% of page weight (4.5 MiB of 5.2 MiB)
Info::
Third-party blocking time is low (0 ms)
86%
First-party Third-party
F
JS Execution Cost
Action
27115ms total JS execution
FIX
27115ms total JS execution
Warning::
https://cf.bstatic.com/psb/capla/static/js/client....: 9139ms CPU time
Warning::
Unattributable: 4924ms CPU time
Warning::
https://www.booking.com/?chal_t=1775320711898&forc...: 4125ms CPU time
Warning::
https://d8c14d4960ca.edge.sdk.awswaf.com/d8c14d496...: 1815ms CPU time
Warning::
https://www.booking.com/__challenge_h78IRKX3kpQxSc...: 1418ms CPU time
Warning::
Third-party scripts: 21496ms (79% of total)

Main Thread Breakdown

Script Evaluation 61% Other 13% Script Parsing & Compilation 10% Style & Layout 10%
ScriptTotalScriptingParse/CompileParty
https://cf.bstatic.com/psb/capla/static/js/client.b20bbad3.js9139ms7383ms281ms3rd
Unattributable4924ms2579ms0ms3rd
https://www.booking.com/?chal_t=1775320711898&force_referer=4125ms374ms139ms1st
https://d8c14d4960ca.edge.sdk.awswaf.com/d8c14d4960ca/a18a4859af9c/challenge.js1815ms1461ms238ms3rd
https://www.booking.com/__challenge_h78IRKX3kpQxScCExxShBNwRUlb/d8c14d4960ca/a18a4859af9c/challenge.js1418ms1044ms267ms1st
https://cf.bstatic.com/psb/capla/static/js/c10242aa.4df8644d.chunk.js1154ms1101ms4ms3rd
https://cf.bstatic.com/psb/capla/static/js/remoteEntry.e4dedb9e.client.js746ms741ms4ms3rd
https://cf.bstatic.com/mobile/js/core_cloudfront_sd/89ab0674156f2cd6570d3aef817558331cd894a7.js668ms461ms141ms3rd
https://pagead2.googlesyndication.com/pagead/managed/js/gpt/m202604010101/pubads_impl.js?cb=31097617387ms252ms96ms3rd
https://cdn.cookielaw.org/scripttemplates/202501.2.0/otBannerSdk.js366ms182ms95ms3rd

Showing top 10 of 28 scripts

F
JS Bundles
Action
93 scripts, 1.9 MB unused
FIX
93 scripts, 1.9 MB unused
Warning::
https://d8c14d4960ca.edge.sdk.awswaf.com/d8c14d496...: 291 KB unused (59%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.booking.com/__challenge_h78IRKX3kpQxSc...: 247 KB unused (50%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cf.bstatic.com/psb/capla/static/js/782ad79...: 200 KB unused (89%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cf.bstatic.com/psb/capla/static/js/client....: 178 KB unused (44%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cf.bstatic.com/psb/capla/static/js/02d4036...: 155 KB unused (70%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 1.9 MB
1937 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://d8c14d4960ca.edge.sdk.awswaf.com/d8c14d4960ca/a18a4859af9c/challenge.js495 KB291 KB (59%)✓3rd
https://www.booking.com/__challenge_h78IRKX3kpQxScCExxShBNwRUlb/d8c14d4960ca/a18a4859af9c/challenge.js495 KB247 KB (50%)✓1st
https://cf.bstatic.com/psb/capla/static/js/782ad794.ea2f5e5f.chunk.js224 KB200 KB (89%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/client.b20bbad3.js409 KB178 KB (44%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/02d40367.dbdf1114.chunk.js223 KB155 KB (70%)✓3rd
https://cf.bstatic.com/mobile/js/core_cloudfront_sd/89ab0674156f2cd6570d3aef817558331cd894a7.js177 KB137 KB (77%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/81da5f32.6979dec3.chunk.js123 KB111 KB (90%)✓3rd
https://pagead2.googlesyndication.com/pagead/managed/js/gpt/m202604010101/pubads_impl.js?cb=31097617182 KB105 KB (58%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/dceb1327.c26ff665.chunk.js122 KB78 KB (64%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/dc32f6b7.6d16fe38.chunk.js159 KB76 KB (48%)✓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

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

F
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
No Cache-Control header found
Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

C
Image Optimization
Action
38 images, 0 KB saveable
REVIEW
38 images, 0 KB saveable
Warning::
https://cf.bstatic.com/mobile/images/gta/iphone_ap... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://t-cf.bstatic.com/design-assets/assets/v3.1... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
38 images 641 KB
0 oversized -0 KB
38 legacy format
2 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

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

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
1 fonts (42 KB)
PASS
1 fonts (42 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

42 KB total

Render-blocking

0

of 1

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s 14.0 s 16.0 s 18.0 s 20.0 s 22.0 s 24.0 s 26.0 s FCP 7.3 s LCP 24.9 shttps://t-cf.bstatic.com/design-assets/assets/v3.155.1/fonts-brand/BookingBold.woffBookingBold.woff https://t-cf.bstatic.com/design-assets/assets/v3.155.1/fonts-brand/BookingBold.woff — 41.6 KiB — 0 ms — font-display: swap
BookingBold.woff woff swap
Size 42 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 ~12 KB and ~24 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
Network Waterfall
304 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
79% of JavaScript execution is third-party
First-party Third-party 21496ms · 2825KB · €233/mo
cf.bstatic.com
Other
Costly
Execution 9139ms
Transfer 409 KB
Unused 44%
Monthly Cost €99/mo
Unattributable
Other
Costly
Execution 4924ms
Transfer 0 KB
Monthly Cost €53/mo
d8c14d4960ca.edge.sdk.awswaf.com
Other
Costly
Execution 1815ms
Transfer 495 KB
Unused 59%
Monthly Cost €20/mo
cf.bstatic.com
Other
Costly
Execution 1154ms
Transfer 6 KB
Monthly Cost €13/mo
cf.bstatic.com
Other
Costly
Execution 746ms
Transfer 7 KB
Monthly Cost €8/mo
cf.bstatic.com
Other
Costly
Execution 668ms
Transfer 177 KB
Unused 77%
Monthly Cost €7/mo
pagead2.googlesyndication.com
Other
Costly
Execution 387ms
Transfer 182 KB
Unused 58%
Monthly Cost €4/mo
OneTrust
Consent
Essential
Execution 366ms
Transfer 114 KB
Unused 60%
Monthly Cost €4/mo
xx.bstatic.com
Other
Costly
Execution 268ms
Transfer 131 KB
Unused 48%
Monthly Cost €3/mo
cf.bstatic.com
Other
Costly
Execution 231ms
Transfer 223 KB
Unused 70%
Monthly Cost €2/mo
OneTrust
Consent
Essential
Execution 215ms
Transfer 3 KB
Monthly Cost €2/mo
cf.bstatic.com
Other
Optional
Execution 169ms
Transfer 159 KB
Unused 48%
Monthly Cost €2/mo
cf.bstatic.com
Other
Optional
Execution 165ms
Transfer 224 KB
Unused 89%
Monthly Cost €2/mo
cf.bstatic.com
Other
Optional
Execution 148ms
Transfer 33 KB
Monthly Cost €2/mo
accounts.google.com
Other
Optional
Execution 144ms
Transfer 93 KB
Unused 75%
Monthly Cost €2/mo
pagead2.googlesyndication.com
Other
Optional
Execution 139ms
Transfer 34 KB
Monthly Cost €2/mo
cf.bstatic.com
Other
Optional
Execution 131ms
Transfer 139 KB
Unused 30%
Monthly Cost €1/mo
cf.bstatic.com
Other
Optional
Execution 113ms
Transfer 122 KB
Unused 64%
Monthly Cost €1/mo
cf.bstatic.com
Other
Optional
Execution 112ms
Transfer 6 KB
Monthly Cost €1/mo
ep2.adtrafficquality.google
Other
Optional
Execution 93ms
Transfer 8 KB
Monthly Cost €1/mo
cf.bstatic.com
Other
Optional
Execution 91ms
Transfer 41 KB
Unused 69%
Monthly Cost €1/mo
cf.bstatic.com
Other
Optional
Execution 82ms
Transfer 69 KB
Unused 49%
Monthly Cost €1/mo
cf.bstatic.com
Other
Optional
Execution 78ms
Transfer 123 KB
Unused 90%
Monthly Cost €1/mo
cf.bstatic.com
Other
Optional
Execution 59ms
Transfer 17 KB
Monthly Cost €1/mo
OneTrust
Consent
Essential
Execution 58ms
Transfer 9 KB
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • cf.bstatic.com adds 9139ms and costs ~€99/month
  • Unattributable adds 4924ms and costs ~€53/month
  • d8c14d4960ca.edge.sdk.awswaf.com adds 1815ms and costs ~€20/month
  • cf.bstatic.com adds 1154ms and costs ~€13/month
  • cf.bstatic.com adds 746ms and costs ~€8/month
  • cf.bstatic.com adds 668ms and costs ~€7/month
  • pagead2.googlesyndication.com adds 387ms and costs ~€4/month
  • xx.bstatic.com adds 268ms and costs ~€3/month
  • cf.bstatic.com adds 231ms and costs ~€2/month

79% 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

cf.bstatic.com takes 9139ms 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

Unattributable takes 4924ms 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

d8c14d4960ca.edge.sdk.awswaf.com takes 1815ms 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

59% of d8c14d4960ca.edge.sdk.awswaf.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

cf.bstatic.com takes 1154ms 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

cf.bstatic.com takes 746ms 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

cf.bstatic.com takes 668ms 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

77% of cf.bstatic.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

pagead2.googlesyndication.com takes 387ms 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

58% of pagead2.googlesyndication.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

60% of OneTrust'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

xx.bstatic.com takes 268ms 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

cf.bstatic.com takes 231ms 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

70% of cf.bstatic.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

89% of cf.bstatic.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

75% of accounts.google.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

64% of cf.bstatic.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

69% of cf.bstatic.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

90% of cf.bstatic.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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