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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
28
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.
96
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.

1.75 s

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

5.93 s

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

1.66 s

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

0.098

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

4.30 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.

6.59 s

Page Load Progression

873 ms
1.7 s
2.6 s
3.5 s
4.4 s
5.2 s
6.1 s
7.0 s
Checks
14
5 PASS 2 REVIEW 5 FIX
F
Page Weight Budget
Action
4.5 MB transferred, 204 requests
FIX
4.5 MB transferred, 204 requests
Critical::
Page weighs 14.4 MB (4.5 MB transferred)
Warning::
JavaScript is 3.5 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 3.5 MB
Warning::
204 HTTP requests — consider bundling or reducing
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Info::
Estimated 0.95 g CO2 per page load
4.5 MB / 2.4 MB budget
4.5 MB transferred
204 requests
0.95 g CO2 per page load
JavaScript 3.5 MiB 77%
Images 727.5 KiB 16%
Other 112.8 KiB 2%
HTML 94.9 KiB 2%
CSS 84.8 KiB 2%
Other 25.0 KiB 1%
Other 23.2 KiB 1%
Other 2.4 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

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 (3.9 MiB of 4.5 MiB)
Info::
Third-party blocking time is low (0 ms)
86%
First-party Third-party
F
JS Execution Cost
Action
5837ms total JS execution
FIX
5837ms total JS execution
Warning::
https://cf.bstatic.com/psb/capla/static/js/client....: 2450ms CPU time
Warning::
https://www.booking.com/?chal_t=1775320755150&forc...: 821ms CPU time
Warning::
Unattributable: 646ms CPU time
Warning::
https://cf.bstatic.com/psb/capla/static/js/782ad79...: 402ms CPU time
Warning::
https://www.booking.com/__challenge_h78IRKX3kpQxSc...: 391ms CPU time
Warning::
Third-party scripts: 4625ms (79% of total)

Main Thread Breakdown

Script Evaluation 61% Other 14% Style & Layout 10% Script Parsing & Compilation 10%
ScriptTotalScriptingParse/CompileParty
https://cf.bstatic.com/psb/capla/static/js/client.b20bbad3.js2450ms1943ms92ms3rd
https://www.booking.com/?chal_t=1775320755150&force_referer=821ms56ms3ms1st
Unattributable646ms150ms0ms3rd
https://cf.bstatic.com/psb/capla/static/js/782ad794.ea2f5e5f.chunk.js402ms342ms57ms3rd
https://www.booking.com/__challenge_h78IRKX3kpQxScCExxShBNwRUlb/d8c14d4960ca/a18a4859af9c/challenge.js391ms271ms60ms1st
https://d8c14d4960ca.edge.sdk.awswaf.com/d8c14d4960ca/a18a4859af9c/challenge.js324ms258ms59ms3rd
https://cf.bstatic.com/psb/capla/static/js/remoteEntry.e4dedb9e.client.js175ms167ms1ms3rd
https://pagead2.googlesyndication.com/pagead/managed/js/gpt/m202604020101/pubads_impl.js?cb=31097618168ms108ms32ms3rd
https://cf.bstatic.com/psb/capla/static/js/node_modules_bookingcom_bui-react_components_BUIProvider_BUIProvider_context_js-_f9a11.2b7c3607.js145ms143ms0ms3rd
https://cf.bstatic.com/psb/capla/static/js/36086793.b1610857.chunk.js119ms103ms0ms3rd

Showing top 10 of 13 scripts

F
JS Bundles
Action
78 scripts, 1.5 MB unused
FIX
78 scripts, 1.5 MB unused
Warning::
https://d8c14d4960ca.edge.sdk.awswaf.com/d8c14d496...: 300 KB unused (59%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cf.bstatic.com/psb/capla/static/js/782ad79...: 196 KB unused (88%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cf.bstatic.com/psb/capla/static/js/client....: 176 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cf.bstatic.com/psb/capla/static/js/c43f530...: 169 KB unused (76%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cf.bstatic.com/psb/capla/static/js/dc32f6b...: 128 KB unused (81%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 1.5 MB
1518 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://d8c14d4960ca.edge.sdk.awswaf.com/d8c14d4960ca/a18a4859af9c/challenge.js506 KB300 KB (59%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/782ad794.ea2f5e5f.chunk.js224 KB196 KB (88%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/client.b20bbad3.js408 KB176 KB (43%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/c43f530f.ac8c6c17.chunk.js222 KB169 KB (76%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/dc32f6b7.6d16fe38.chunk.js159 KB128 KB (81%)✓3rd
https://pagead2.googlesyndication.com/pagead/managed/js/gpt/m202604020101/pubads_impl.js?cb=31097618183 KB104 KB (57%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/dceb1327.c26ff665.chunk.js122 KB78 KB (64%)✓3rd
https://accounts.google.com/gsi/client93 KB70 KB (76%)✓3rd
https://cf.bstatic.com/psb/capla/static/js/81da5f32.6979dec3.chunk.js123 KB69 KB (57%)✓3rd
https://cdn.cookielaw.org/scripttemplates/202501.2.0/otBannerSdk.js114 KB69 KB (60%)✓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.

B
Image Optimization
33 images, 0 KB saveable
REVIEW
33 images, 0 KB saveable
Info::
All images are well-optimized
33 images 728 KB
0 oversized -0 KB
29 legacy format
0 missing dimensions CLS risk
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
No web fonts (system fonts)
PASS
No web fonts (system fonts)
Info::
No web fonts loaded — system fonts are fastest
No web fonts loaded — system fonts are optimal.
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
204 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 4625ms · 1764KB · €50/mo
cf.bstatic.com
Other
Costly
Execution 2450ms
Transfer 408 KB
Unused 43%
Monthly Cost €27/mo
Unattributable
Other
Costly
Execution 646ms
Transfer 0 KB
Monthly Cost €7/mo
cf.bstatic.com
Other
Costly
Execution 402ms
Transfer 224 KB
Unused 88%
Monthly Cost €4/mo
d8c14d4960ca.edge.sdk.awswaf.com
Other
Costly
Execution 324ms
Transfer 506 KB
Unused 59%
Monthly Cost €4/mo
cf.bstatic.com
Other
Optional
Execution 175ms
Transfer 7 KB
Monthly Cost €2/mo
pagead2.googlesyndication.com
Other
Optional
Execution 168ms
Transfer 183 KB
Unused 57%
Monthly Cost €2/mo
cf.bstatic.com
Other
Optional
Execution 145ms
Transfer 1 KB
Monthly Cost €2/mo
cf.bstatic.com
Other
Optional
Execution 119ms
Transfer 3 KB
Monthly Cost €1/mo
OneTrust
Consent
Essential
Execution 91ms
Transfer 114 KB
Unused 60%
Monthly Cost €1/mo
accounts.google.com
Other
Optional
Execution 54ms
Transfer 93 KB
Unused 76%
Monthly Cost €1/mo
cf.bstatic.com
Other
Optional
Execution 52ms
Transfer 222 KB
Unused 76%
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • cf.bstatic.com adds 2450ms and costs ~€27/month
  • Unattributable adds 646ms and costs ~€7/month
  • cf.bstatic.com adds 402ms and costs ~€4/month
  • d8c14d4960ca.edge.sdk.awswaf.com adds 324ms and costs ~€4/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 2450ms 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 646ms 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 402ms 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

88% 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

d8c14d4960ca.edge.sdk.awswaf.com takes 324ms 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

57% 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

76% 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

76% 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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