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https://amazon.co.jp

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
87
GRADE
B
FIX
2
REVIEW
4
PASS
9
INFO
2

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

Mobile Desktop
53
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.
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.

5.88 s

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

5.97 s

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

430 ms

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

0.000

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

5.88 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.

6.45 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
17
9 PASS 4 REVIEW 2 FIX
D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (581.4 KiB of 581.6 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
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
JS Execution Cost
Action
1215ms total JS execution
REVIEW
1215ms total JS execution
Warning::
https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awsw...: 762ms CPU time
Warning::
Unattributable: 259ms CPU time
Info::
https://www.amazon.co.jp/: 122ms CPU time
Info::
https://images-na.ssl-images-amazon.com/images/G/0...: 73ms CPU time
Warning::
Third-party scripts: 1215ms (100% of total)

Main Thread Breakdown

Script Evaluation 63% Other 17% Script Parsing & Compilation 13% Style & Layout 4%
ScriptTotalScriptingParse/CompileParty
https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/challenge.js762ms551ms158ms3rd
Unattributable259ms119ms0ms3rd
https://www.amazon.co.jp/122ms47ms4ms3rd
https://images-na.ssl-images-amazon.com/images/G/01/AUIClients/ClientSideMetricsAUIJavascript-51171fbdd28e1a7a61e922e8f0272af8bc74d37b.secure.variant-desktop-session-snapshot-keypress.min._V2_.js73ms52ms2ms3rd
C
JS Bundles
Action
5 scripts, 280 KB unused
REVIEW
5 scripts, 280 KB unused
Warning::
https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awsw...: 280 KB unused (56%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 280 KB
280 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/challenge.js501 KB280 KB (56%)✓3rd
https://images-fe.ssl-images-amazon.com/images/G/01/csminstrumentation/csm-captcha-instrumentation.min.js1 KB—✓3rd
https://images-fe.ssl-images-amazon.com/images/G/01/csminstrumentation/rd-script-6d68177fa6061598e9509dc4b5bdd08d.js1 KB—✓3rd
https://images-na.ssl-images-amazon.com/images/G/01/csminstrumentation/ue-base-1c399ad9886cab69575e1e5ee15c61a1._V313498596_.js4 KB—✓3rd
https://images-na.ssl-images-amazon.com/images/G/01/AUIClients/ClientSideMetricsAUIJavascript-51171fbdd28e1a7a61e922e8f0272af8bc74d37b.secure.variant-desktop-session-snapshot-keypress.min._V2_.js8 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

B
Page Weight Inventory
17 resources · 582 KB · 280 KB savings available
REVIEW
17 resources · 582 KB · 280 KB savings available
Info::
Within 1MB page-weight target
Got: 582 KB
Info::
~280 KB of savings available
Warning::
16 third-party resources (100% of weight)
Info::
1 resources over 200KB
17 resources · 581.6 KiB · 16 third-party Within 1MB page-weight target
JavaScript 89% · 515.6 KiB
Image 6% · 35.5 KiB
CSS 4% · 23.5 KiB
Document 1% · 4.8 KiB
Other 0% · 2.2 KiB

~280.1 KiB of savings available

Remove unused JavaScript: 280.1 KiB
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Page Weight Budget
582 KB transferred, 17 requests
PASS
582 KB transferred, 17 requests
Info::
Page weighs 1.6 MB (582 KB transferred)
Warning::
JavaScript is 516 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 516 KB
Info::
17 HTTP requests
Info::
Estimated 0.12 g CO2 per page load
582 KB / 2.4 MB budget
582 KB transferred
17 requests
0.12 g CO2 per page load
JavaScript 515.6 KiB 89%
CSS 23.5 KiB 4%
Other 18.1 KiB 3%
Images 17.6 KiB 3%
HTML 4.6 KiB 1%
Other 2.0 KiB 0%
Other 177 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
2 images, 0 KB saveable
PASS
2 images, 0 KB saveable
Warning::
https://fls-fe.amazon.co.jp/1/oc-csi/1/OP/requestI... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
2 images 18 KB
0 oversized -0 KB
2 legacy format
1 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

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
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
Network Waterfall
17 requests over 2846ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s 6.0 s FCP 5.9 s LCP 6.0 shttps://amazon.co.jp// https://amazon.co.jp/ — 301 — 201 B — 529 ms — http/1.1https://www.amazon.co.jp/www.amazon.co.jp/ https://www.amazon.co.jp/ — 202 — 2.4 KiB — 65 ms — h2https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/challenge.js1c5c1ecf7303.742a0c6e.eu-west-3.tok... https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/challenge.js — 200 — 501.3 KiB — 159 ms — h2https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/inputs?client=browser1c5c1ecf7303.742a0c6e.eu-west-3.tok... https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/inputs?client=browser — 200 — 828 B — 52 ms — h3https://www.amazon.co.jp/favicon.icowww.amazon.co.jp/favicon.ico https://www.amazon.co.jp/favicon.ico — 200 — 17.9 KiB — 23 ms — h2https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/mp_verify1c5c1ecf7303.742a0c6e.eu-west-3.tok... https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/mp_verify — 200 — 635 B — 38 ms — h3https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/mp_verify1c5c1ecf7303.742a0c6e.eu-west-3.tok... https://1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com/1c5c1ecf7303/68f86b376542/d807fcba4336/mp_verify — 200 — 633 B — 38 ms — h3https://www.amazon.co.jp/www.amazon.co.jp/ https://www.amazon.co.jp/ — 200 — 2.2 KiB — 166 ms — h3https://images-na.ssl-images-amazon.com/images/G/01/AUIClients/AmazonUI-3c913031596ca78a3768f4e934b1cc02ce238101.secure.min._V1_.cssimages-na.ssl-images-amazon.com/ima... https://images-na.ssl-images-amazon.com/images/G/01/AUIClients/AmazonUI-3c913031596ca78a3768f4e934b1cc02ce238101.secure.min._V1_.css — 200 — 23.5 KiB — 115 ms — h2https://fls-fe.amazon.co.jp/1/oc-csi/1/OP/requestId=QTASCVQFZF7BAFR1HMW3&js=1fls-fe.amazon.co.jp/1/oc-csi/1/OP/r... https://fls-fe.amazon.co.jp/1/oc-csi/1/OP/requestId=QTASCVQFZF7BAFR1HMW3&js=1 — 200 — 150 B — 612 ms — h2https://images-fe.ssl-images-amazon.com/images/G/01/csminstrumentation/csm-captcha-instrumentation.min.jsimages-fe.ssl-images-amazon.com/ima... https://images-fe.ssl-images-amazon.com/images/G/01/csminstrumentation/csm-captcha-instrumentation.min.js — 200 — 1.2 KiB — 53 ms — h2https://images-fe.ssl-images-amazon.com/images/G/01/csminstrumentation/rd-script-6d68177fa6061598e9509dc4b5bdd08d.jsimages-fe.ssl-images-amazon.com/ima... https://images-fe.ssl-images-amazon.com/images/G/01/csminstrumentation/rd-script-6d68177fa6061598e9509dc4b5bdd08d.js — 200 — 822 B — 53 ms — h2https://images-na.ssl-images-amazon.com/images/G/01/amazonui/sprites/aui_sprite_0007-1x._V383827579_.pngimages-na.ssl-images-amazon.com/ima... https://images-na.ssl-images-amazon.com/images/G/01/amazonui/sprites/aui_sprite_0007-1x._V383827579_.png — 200 — 17.4 KiB — 23 ms — h2https://images-na.ssl-images-amazon.com/images/G/01/csminstrumentation/ue-base-1c399ad9886cab69575e1e5ee15c61a1._V313498596_.jsimages-na.ssl-images-amazon.com/ima... https://images-na.ssl-images-amazon.com/images/G/01/csminstrumentation/ue-base-1c399ad9886cab69575e1e5ee15c61a1._V313498596_.js — 200 — 3.8 KiB — 21 ms — h3https://images-na.ssl-images-amazon.com/images/G/01/AUIClients/ClientSideMetricsAUIJavascript-51171fbdd28e1a7a61e922e8f0272af8bc74d37b.secure.variant-desktop-session-snapshot-keypress.min._V2_.jsimages-na.ssl-images-amazon.com/ima... https://images-na.ssl-images-amazon.com/images/G/01/AUIClients/ClientSideMetricsAUIJavascript-51171fbdd28e1a7a61e922e8f0272af8bc74d37b.secure.variant-desktop-session-snapshot-keypress.min._V2_.js — 200 — 8.5 KiB — 21 ms — h3https://www.amazon.co.jp/favicon.icowww.amazon.co.jp/favicon.ico https://www.amazon.co.jp/favicon.ico — 200 — 0 B — 1 ms — h2https://fls-fe.amazon.co.jp/1/batch/1/OE/fls-fe.amazon.co.jp/1/batch/1/OE/ https://fls-fe.amazon.co.jp/1/batch/1/OE/ — 204 — 177 B — 363 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
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 1215ms · 512KB · ¥1679/mo
1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com
Other
Costly
Execution 762ms
Transfer 501 KB
Unused 56%
Monthly Cost ¥1052/mo
Unattributable
Other
Costly
Execution 259ms
Transfer 0 KB
Monthly Cost ¥358/mo
www.amazon.co.jp
Other
Costly
Execution 122ms
Transfer 2 KB
Monthly Cost ¥168/mo
images-na.ssl-images-amazon.com
Other
Costly
Execution 73ms
Transfer 8 KB
Monthly Cost ¥101/mo

These scripts may cost more than they're worth

  • 1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com adds 762ms and costs ~¥1052/month
  • Unattributable adds 259ms and costs ~¥358/month
  • www.amazon.co.jp adds 122ms and costs ~¥168/month
  • images-na.ssl-images-amazon.com adds 73ms and costs ~¥101/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

1c5c1ecf7303.742a0c6e.eu-west-3.token.awswaf.com takes 762ms 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

56% of 1c5c1ecf7303.742a0c6e.eu-west-3.token.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

Unattributable 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

www.amazon.co.jp takes 122ms 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

images-na.ssl-images-amazon.com takes 73ms 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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