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https://www.nikkei.com

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
77
GRADE
C
FIX
2
REVIEW
5
PASS
5
INFO
2

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

Mobile Desktop
89
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
90
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
92
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.

451 ms

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

1.56 s

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

70 ms

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

0.083

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

2.03 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.

1.59 s

Page Load Progression

518 ms
1.0 s
1.6 s
2.1 s
2.6 s
3.1 s
3.6 s
4.1 s
Checks
14
5 PASS 5 REVIEW 2 FIX
F
Page Weight Budget
Action
3.2 MB transferred, 148 requests
FIX
3.2 MB transferred, 148 requests
Warning::
Page weighs 12.1 MB (3.2 MB transferred)
Warning::
Images are 2.3 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 2.3 MB
Warning::
148 HTTP requests — consider bundling or reducing
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Info::
Estimated 0.67 g CO2 per page load
3.2 MB / 2.4 MB budget
3.2 MB transferred
148 requests
0.67 g CO2 per page load
Images 2.3 MiB 72%
JavaScript 406.1 KiB 12%
Other 376.1 KiB 11%
HTML 94.2 KiB 3%
CSS 25.9 KiB 1%
Other 2.2 KiB 0%
0 2.4 MB 4.9 MB
Over budget

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Why this matters

Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.

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
91% third-party, 0 ms blocking
FIX
91% third-party, 0 ms blocking
Warning::
Third-party code accounts for 91% of page weight (2.9 MiB of 3.2 MiB)
Info::
Third-party blocking time is low (0 ms)
91%
First-party Third-party
C
Image Optimization
Action
105 images, 0 KB saveable
REVIEW
105 images, 0 KB saveable
Warning::
https://www.nikkei.com/.resources/k-components/ico... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.nikkei.com/.resources/k-components/ico... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.nikkei.com/.resources/k-components/ico... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://partsa.nikkei.com/parts/ds/images/topic/ba... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.nikkei.com/.resources/k-components/log... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.nikkei.com/.resources/k-components/ico... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
105 images 2.3 MB
0 oversized -0 KB
31 legacy format
6 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

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

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
JS Execution Cost
Action
1083ms total JS execution
REVIEW
1083ms total JS execution
Warning::
https://www.nikkei.com/: 620ms CPU time
Warning::
Unattributable: 303ms CPU time
Info::
https://www.nikkei.com/.resources/k2-top/main.rev-...: 90ms CPU time
Info::
https://www.nikkei.com/.resources/tracking/static/...: 70ms CPU time
Info::
Third-party scripts: 303ms (28% of total)

Main Thread Breakdown

Style & Layout 44% Other 26% Script Evaluation 22%
ScriptTotalScriptingParse/CompileParty
https://www.nikkei.com/620ms4ms1ms1st
Unattributable303ms41ms0ms3rd
https://www.nikkei.com/.resources/k2-top/main.rev-4d78526c.js90ms81ms1ms1st
https://www.nikkei.com/.resources/tracking/static/atlas/atj.min.rev-c6c444.js70ms22ms1ms1st
C
JS Bundles
Action
20 scripts, 186 KB unused
REVIEW
20 scripts, 186 KB unused
Warning::
https://www.nikkei.com/.resources/k2-top/main.rev-...: 51 KB unused (39%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://static.cmp.datasign.co/v2/assets/cmp_ui.js...: 45 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://static.cmp.datasign.co/v2/assets/cmp_ui.js...: 45 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://connect.facebook.net/en_US/fbevents.js: 44 KB unused (47%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 186 KB
186 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.nikkei.com/.resources/k2-top/main.rev-4d78526c.js134 KB51 KB (39%)✓1st
https://static.cmp.datasign.co/v2/assets/cmp_ui.js?h=f4f2249aa9106 KB45 KB (43%)✓3rd
https://static.cmp.datasign.co/v2/assets/cmp_ui.js?h=f4f2249aa90 KB45 KB (43%)✓3rd
https://connect.facebook.net/en_US/fbevents.js95 KB44 KB (47%)✓3rd
https://www.nikkei.com/.resources/tracking/static/atlas/link-tracking.rev-c01db9.js1 KB—✓1st
https://www.nikkei.com/.resources/tracking/static/atlas/google-analytics.rev-896d69.js1 KB—✓1st
https://cmp.datasign.co/v2/f4f2249aa9/cmp.js0 KB—✓3rd
https://www.nikkei.com/.resources/tracking/static/atlas/init-rntrack-vars.rev-6357d1.js0 KB—✓1st
https://www.nikkei.com/.resources/tracking/static/atlas/atj.min.rev-c6c444.js7 KB—✓1st
https://www.nikkei.com/.resources/tracking/static/atlas/c2p.rev-8c9198.js2 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

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

Green Hosting

No green hosting detected

B
HTTP Caching
no-cache
REVIEW
no-cache
Info::
Cache-Control header is set
Got: no-cache
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

no-cache

DirectiveValueMeaning
no-cache—Cache but always revalidate first
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
148 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
28% of JavaScript execution is third-party
First-party Third-party 303ms · 0KB · ¥418/mo
Unattributable
Other
Costly
Execution 303ms
Transfer 0 KB
Monthly Cost ¥418/mo

These scripts may cost more than they're worth

  • Unattributable adds 303ms and costs ~¥418/month

Unattributable takes 303ms 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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