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https://ndl.go.jp

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
72
GRADE
C
FIX
6
REVIEW
2
PASS
7
INFO
2

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

Mobile Desktop
31
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
85
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.

8.64 s

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

17.64 s

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

382 ms

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

0.340

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

8.64 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.

17.66 s

Page Load Progression

607 ms
1.2 s
1.8 s
2.4 s
3.0 s
3.6 s
4.2 s
4.9 s
Checks
17
7 PASS 2 REVIEW 6 FIX
F
Page Weight Budget
Action
3.5 MB transferred, 35 requests
FIX
3.5 MB transferred, 35 requests
Warning::
Page weighs 5.9 MB (3.5 MB transferred)
Warning::
Images are 1.4 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 1.4 MB
Warning::
JavaScript is 1.1 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.1 MB
Info::
Fonts are 898 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 898 KB
Info::
35 HTTP requests
Info::
Estimated 0.73 g CO2 per page load
3.5 MB / 2.4 MB budget
3.5 MB transferred
35 requests
0.73 g CO2 per page load
Images 1.4 MiB 40%
JavaScript 1.1 MiB 31%
Fonts 897.8 KiB 25%
HTML 55.1 KiB 2%
CSS 41.4 KiB 1%
Other 36.4 KiB 1%
Other 11.1 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

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

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

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 (3.5 MiB of 3.5 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Execution Cost
Action
2437ms total JS execution
FIX
2437ms total JS execution
Warning::
Unattributable: 963ms CPU time
Warning::
https://www.ndl.go.jp/_nuxt/xQirD6gr.js: 898ms CPU time
Warning::
https://www.ndl.go.jp/: 576ms CPU time
Warning::
Third-party scripts: 2437ms (100% of total)

Main Thread Breakdown

Script Evaluation 50% Other 23% Style & Layout 20% Rendering 4%
ScriptTotalScriptingParse/CompileParty
Unattributable963ms483ms0ms3rd
https://www.ndl.go.jp/_nuxt/xQirD6gr.js898ms725ms7ms3rd
https://www.ndl.go.jp/576ms22ms1ms3rd
D
JS Bundles
Action
7 scripts, 465 KB unused
FIX
7 scripts, 465 KB unused
Warning::
https://www.ndl.go.jp/_nuxt/xQirD6gr.js: 465 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 465 KB
465 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.ndl.go.jp/_nuxt/xQirD6gr.js1113 KB465 KB (43%)✓3rd
https://www.ndl.go.jp/_nuxt/vDxNIUDS.js6 KB—✓3rd
https://www.ndl.go.jp/_nuxt/B8Ocx6Fi.js2 KB—✓3rd
https://www.ndl.go.jp/_nuxt/Ccz9fvUb.js2 KB—✓3rd
https://www.ndl.go.jp/_nuxt/BJMw6gLR.js15 KB—✓3rd
https://www.ndl.go.jp/_nuxt/CIR4OTlF.js6 KB—✓3rd
https://www.ndl.go.jp/_nuxt/DOPaxgQJ.js2 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

F
Page Weight Inventory
Action
35 resources · 3.5 MB · 465 KB savings available
FIX
35 resources · 3.5 MB · 465 KB savings available
Warning::
Page weight 2.5 MB over 1MB target
Got: 3.5 MB Expected: ≤ 1 MB
Info::
~465 KB of savings available
Warning::
34 third-party resources (100% of weight)
Info::
6 resources over 200KB
35 resources · 3.5 MiB · 34 third-party 2.5 MiB over 1MB target
Image 40% · 1.4 MiB
JavaScript 32% · 1.1 MiB
Font 25% · 897.8 KiB
Document 2% · 55.2 KiB
CSS 1% · 47.0 KiB
Other 0% · 12.3 KiB

~464.9 KiB of savings available

Remove unused JavaScript: 464.9 KiB
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
9 images, 0 KB saveable
REVIEW
9 images, 0 KB saveable
Warning::
https://www.ndl.go.jp/file/part/top/pickups/main_j... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ndl.go.jp/assets/images/naiic.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ndl.go.jp/assets/images/brand/x.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ndl.go.jp/assets/images/brand/youtube.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
9 images 1.4 MB
0 oversized -0 KB
3 legacy format
4 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

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
3 fonts (898 KB)
PASS
3 fonts (898 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

898 KB total

Render-blocking

0

of 3

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 FCP 8.6 s LCP 17.6 shttps://www.ndl.go.jp/assets/fonts/NotoSansJP-Regular.woff2NotoSansJP-Regular.woff2 https://www.ndl.go.jp/assets/fonts/NotoSansJP-Regular.woff2 — 296.2 KiB — 1.6 s — font-display: swaphttps://www.ndl.go.jp/assets/fonts/NotoSansJP-Medium.woff2NotoSansJP-Medium.woff2 https://www.ndl.go.jp/assets/fonts/NotoSansJP-Medium.woff2 — 299.6 KiB — 1.6 s — font-display: swaphttps://www.ndl.go.jp/assets/fonts/NotoSansJP-Bold.woff2NotoSansJP-Bold.woff2 https://www.ndl.go.jp/assets/fonts/NotoSansJP-Bold.woff2 — 302.0 KiB — 1.5 s — font-display: swap
NotoSansJP-Regular.woff2 woff2 swap
Size 296 KB
Load time 1.6 s
Start 1.4 s
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
NotoSansJP-Medium.woff2 woff2 swap
Size 300 KB
Load time 1.6 s
Start 1.4 s
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
NotoSansJP-Bold.woff2 woff2 swap
Size 302 KB
Load time 1.5 s
Start 1.4 s
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
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 ~449 KB and ~898 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
7 hints, 0 missing preconnects
PASS
7 hints, 0 missing preconnects
Info::
Page uses 7 resource hint(s)

Current Resource Hints

preconnect
—
preload
1
dns-prefetch
—
prefetch
6

7 resource hints configured

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
35 requests over 5433ms
INFO
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 FCP 8.6 s LCP 17.6 shttps://ndl.go.jp// https://ndl.go.jp/ — 301 — 84 B — 669 ms — h2https://www.ndl.go.jp/www.ndl.go.jp/ https://www.ndl.go.jp/ — 200 — 55.1 KiB — 609 ms — h2https://www.ndl.go.jp/_nuxt/entry.BvlraQy1.csswww.ndl.go.jp/_nuxt/entry.BvlraQy1.... https://www.ndl.go.jp/_nuxt/entry.BvlraQy1.css — 200 — 37.4 KiB — 36 ms — h2https://www.ndl.go.jp/_nuxt/index.CVPa9HsH.csswww.ndl.go.jp/_nuxt/index.CVPa9HsH.... https://www.ndl.go.jp/_nuxt/index.CVPa9HsH.css — 200 — 2.6 KiB — 66 ms — h2https://www.ndl.go.jp/_nuxt/xQirD6gr.jswww.ndl.go.jp/_nuxt/xQirD6gr.js https://www.ndl.go.jp/_nuxt/xQirD6gr.js — 200 — 1.1 MiB — 99 ms — h2https://www.ndl.go.jp/_nuxt/vDxNIUDS.jswww.ndl.go.jp/_nuxt/vDxNIUDS.js https://www.ndl.go.jp/_nuxt/vDxNIUDS.js — 200 — 5.9 KiB — 65 ms — h2https://www.ndl.go.jp/_nuxt/builds/meta/84d4c2ec-2030-4aed-a224-eb8ed732263f.jsonwww.ndl.go.jp/_nuxt/builds/meta/84d... https://www.ndl.go.jp/_nuxt/builds/meta/84d4c2ec-2030-4aed-a224-eb8ed732263f.json — 200 — 1.3 KiB — 69 ms — h2https://www.ndl.go.jp/_nuxt/B8Ocx6Fi.jswww.ndl.go.jp/_nuxt/B8Ocx6Fi.js https://www.ndl.go.jp/_nuxt/B8Ocx6Fi.js — 200 — 1.8 KiB — 69 ms — h2https://www.ndl.go.jp/_nuxt/Ccz9fvUb.jswww.ndl.go.jp/_nuxt/Ccz9fvUb.js https://www.ndl.go.jp/_nuxt/Ccz9fvUb.js — 200 — 1.9 KiB — 68 ms — h2https://www.ndl.go.jp/_nuxt/SearchBibMinaPart.DtbgFeXm.csswww.ndl.go.jp/_nuxt/SearchBibMinaPa... https://www.ndl.go.jp/_nuxt/SearchBibMinaPart.DtbgFeXm.css — 200 — 3.4 KiB — 68 ms — h2https://www.ndl.go.jp/_nuxt/BJMw6gLR.jswww.ndl.go.jp/_nuxt/BJMw6gLR.js https://www.ndl.go.jp/_nuxt/BJMw6gLR.js — 200 — 15.3 KiB — 67 ms — h2https://www.ndl.go.jp/_nuxt/CmsSearchJson.BWu3Uw2V.csswww.ndl.go.jp/_nuxt/CmsSearchJson.B... https://www.ndl.go.jp/_nuxt/CmsSearchJson.BWu3Uw2V.css — 200 — 2.1 KiB — 68 ms — h2https://www.ndl.go.jp/_nuxt/CIR4OTlF.jswww.ndl.go.jp/_nuxt/CIR4OTlF.js https://www.ndl.go.jp/_nuxt/CIR4OTlF.js — 200 — 6.2 KiB — 68 ms — h2https://www.ndl.go.jp/file/part/top/pickups/main_jp.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/main_jp.webp — 200 — 172.9 KiB — 3.5 s — h2https://www.ndl.go.jp/file/part/top/pickups/jikihitsu_pickup.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/jikihitsu_pickup.webp — 200 — 63.0 KiB — 3.2 s — h2https://www.ndl.go.jp/file/part/top/pickups/R7kagipro.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/R7kagipro.webp — 200 — 551.3 KiB — 3.9 s — h2https://www.ndl.go.jp/file/part/top/pickups/warp_pickup.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/warp_pickup.webp — 200 — 127.8 KiB — 3.4 s — h2https://www.ndl.go.jp/file/part/top/pickups/hinagiku_renewal_jp.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/hinagiku_renewal_jp.webp — 200 — 57.1 KiB — 3.4 s — h2https://www.ndl.go.jp/file/part/top/pickups/bib_search.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/bib_search.webp — 200 — 391.4 KiB — 3.2 s — h2https://www.ndl.go.jp/assets/images/naiic.pngwww.ndl.go.jp/assets/images/naiic.p... https://www.ndl.go.jp/assets/images/naiic.png — 200 — 13.4 KiB — 912 ms — h2https://www.ndl.go.jp/assets/images/brand/x.pngwww.ndl.go.jp/assets/images/brand/x... https://www.ndl.go.jp/assets/images/brand/x.png — 200 — 2.6 KiB — 699 ms — h2https://www.ndl.go.jp/assets/images/brand/youtube.pngwww.ndl.go.jp/assets/images/brand/y... https://www.ndl.go.jp/assets/images/brand/youtube.png — 200 — 42.5 KiB — 1.1 s — h2https://www.ndl.go.jp/assets/fonts/NotoSansJP-Regular.woff2www.ndl.go.jp/assets/fonts/NotoSans... https://www.ndl.go.jp/assets/fonts/NotoSansJP-Regular.woff2 — 200 — 296.2 KiB — 1.6 s — h3https://www.ndl.go.jp/assets/fonts/NotoSansJP-Medium.woff2www.ndl.go.jp/assets/fonts/NotoSans... https://www.ndl.go.jp/assets/fonts/NotoSansJP-Medium.woff2 — 200 — 299.6 KiB — 1.6 s — h3https://www.ndl.go.jp/assets/fonts/NotoSansJP-Bold.woff2www.ndl.go.jp/assets/fonts/NotoSans... https://www.ndl.go.jp/assets/fonts/NotoSansJP-Bold.woff2 — 200 — 302.0 KiB — 1.5 s — h3https://www.ndl.go.jp/api/session/uaawww.ndl.go.jp/api/session/uaa https://www.ndl.go.jp/api/session/uaa — 200 — 1.0 KiB — 945 ms — h3https://www.ndl.go.jp/api/page/hp/search-news?tag=News&size=6www.ndl.go.jp/api/page/hp/search-ne... https://www.ndl.go.jp/api/page/hp/search-news?tag=News&size=6 — 200 — 4.3 KiB — 718 ms — h3https://www.ndl.go.jp/api/calendar?lib=TML&from=1775001600000&to=1777507200000www.ndl.go.jp/api/calendar?lib=TML&... https://www.ndl.go.jp/api/calendar?lib=TML&from=1775001600000&to=1777507200000 — 200 — 1.2 KiB — 490 ms — h3https://www.ndl.go.jp/api/calendar?lib=KSK&from=1775001600000&to=1777507200000www.ndl.go.jp/api/calendar?lib=KSK&... https://www.ndl.go.jp/api/calendar?lib=KSK&from=1775001600000&to=1777507200000 — 200 — 1.2 KiB — 1.9 s — h3https://www.ndl.go.jp/api/calendar?lib=ILCL&from=1775001600000&to=1777507200000www.ndl.go.jp/api/calendar?lib=ILCL... https://www.ndl.go.jp/api/calendar?lib=ILCL&from=1775001600000&to=1777507200000 — 200 — 1.2 KiB — 486 ms — h3
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 FCP 8.6 s LCP 17.6 shttps://ndl.go.jp// https://ndl.go.jp/ — 301 — 84 B — 669 ms — h2https://www.ndl.go.jp/www.ndl.go.jp/ https://www.ndl.go.jp/ — 200 — 55.1 KiB — 609 ms — h2https://www.ndl.go.jp/_nuxt/entry.BvlraQy1.csswww.ndl.go.jp/_nuxt/entry.BvlraQy1.... https://www.ndl.go.jp/_nuxt/entry.BvlraQy1.css — 200 — 37.4 KiB — 36 ms — h2https://www.ndl.go.jp/_nuxt/index.CVPa9HsH.csswww.ndl.go.jp/_nuxt/index.CVPa9HsH.... https://www.ndl.go.jp/_nuxt/index.CVPa9HsH.css — 200 — 2.6 KiB — 66 ms — h2https://www.ndl.go.jp/_nuxt/xQirD6gr.jswww.ndl.go.jp/_nuxt/xQirD6gr.js https://www.ndl.go.jp/_nuxt/xQirD6gr.js — 200 — 1.1 MiB — 99 ms — h2https://www.ndl.go.jp/_nuxt/vDxNIUDS.jswww.ndl.go.jp/_nuxt/vDxNIUDS.js https://www.ndl.go.jp/_nuxt/vDxNIUDS.js — 200 — 5.9 KiB — 65 ms — h2https://www.ndl.go.jp/_nuxt/builds/meta/84d4c2ec-2030-4aed-a224-eb8ed732263f.jsonwww.ndl.go.jp/_nuxt/builds/meta/84d... https://www.ndl.go.jp/_nuxt/builds/meta/84d4c2ec-2030-4aed-a224-eb8ed732263f.json — 200 — 1.3 KiB — 69 ms — h2https://www.ndl.go.jp/_nuxt/B8Ocx6Fi.jswww.ndl.go.jp/_nuxt/B8Ocx6Fi.js https://www.ndl.go.jp/_nuxt/B8Ocx6Fi.js — 200 — 1.8 KiB — 69 ms — h2https://www.ndl.go.jp/_nuxt/Ccz9fvUb.jswww.ndl.go.jp/_nuxt/Ccz9fvUb.js https://www.ndl.go.jp/_nuxt/Ccz9fvUb.js — 200 — 1.9 KiB — 68 ms — h2https://www.ndl.go.jp/_nuxt/SearchBibMinaPart.DtbgFeXm.csswww.ndl.go.jp/_nuxt/SearchBibMinaPa... https://www.ndl.go.jp/_nuxt/SearchBibMinaPart.DtbgFeXm.css — 200 — 3.4 KiB — 68 ms — h2https://www.ndl.go.jp/_nuxt/BJMw6gLR.jswww.ndl.go.jp/_nuxt/BJMw6gLR.js https://www.ndl.go.jp/_nuxt/BJMw6gLR.js — 200 — 15.3 KiB — 67 ms — h2https://www.ndl.go.jp/_nuxt/CmsSearchJson.BWu3Uw2V.csswww.ndl.go.jp/_nuxt/CmsSearchJson.B... https://www.ndl.go.jp/_nuxt/CmsSearchJson.BWu3Uw2V.css — 200 — 2.1 KiB — 68 ms — h2https://www.ndl.go.jp/_nuxt/CIR4OTlF.jswww.ndl.go.jp/_nuxt/CIR4OTlF.js https://www.ndl.go.jp/_nuxt/CIR4OTlF.js — 200 — 6.2 KiB — 68 ms — h2https://www.ndl.go.jp/file/part/top/pickups/main_jp.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/main_jp.webp — 200 — 172.9 KiB — 3.5 s — h2https://www.ndl.go.jp/file/part/top/pickups/jikihitsu_pickup.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/jikihitsu_pickup.webp — 200 — 63.0 KiB — 3.2 s — h2https://www.ndl.go.jp/file/part/top/pickups/R7kagipro.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/R7kagipro.webp — 200 — 551.3 KiB — 3.9 s — h2https://www.ndl.go.jp/file/part/top/pickups/warp_pickup.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/warp_pickup.webp — 200 — 127.8 KiB — 3.4 s — h2https://www.ndl.go.jp/file/part/top/pickups/hinagiku_renewal_jp.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/hinagiku_renewal_jp.webp — 200 — 57.1 KiB — 3.4 s — h2https://www.ndl.go.jp/file/part/top/pickups/bib_search.webpwww.ndl.go.jp/file/part/top/pickups... https://www.ndl.go.jp/file/part/top/pickups/bib_search.webp — 200 — 391.4 KiB — 3.2 s — h2https://www.ndl.go.jp/assets/images/naiic.pngwww.ndl.go.jp/assets/images/naiic.p... https://www.ndl.go.jp/assets/images/naiic.png — 200 — 13.4 KiB — 912 ms — h2https://www.ndl.go.jp/assets/images/brand/x.pngwww.ndl.go.jp/assets/images/brand/x... https://www.ndl.go.jp/assets/images/brand/x.png — 200 — 2.6 KiB — 699 ms — h2https://www.ndl.go.jp/assets/images/brand/youtube.pngwww.ndl.go.jp/assets/images/brand/y... https://www.ndl.go.jp/assets/images/brand/youtube.png — 200 — 42.5 KiB — 1.1 s — h2https://www.ndl.go.jp/assets/fonts/NotoSansJP-Regular.woff2www.ndl.go.jp/assets/fonts/NotoSans... https://www.ndl.go.jp/assets/fonts/NotoSansJP-Regular.woff2 — 200 — 296.2 KiB — 1.6 s — h3https://www.ndl.go.jp/assets/fonts/NotoSansJP-Medium.woff2www.ndl.go.jp/assets/fonts/NotoSans... https://www.ndl.go.jp/assets/fonts/NotoSansJP-Medium.woff2 — 200 — 299.6 KiB — 1.6 s — h3https://www.ndl.go.jp/assets/fonts/NotoSansJP-Bold.woff2www.ndl.go.jp/assets/fonts/NotoSans... https://www.ndl.go.jp/assets/fonts/NotoSansJP-Bold.woff2 — 200 — 302.0 KiB — 1.5 s — h3https://www.ndl.go.jp/api/session/uaawww.ndl.go.jp/api/session/uaa https://www.ndl.go.jp/api/session/uaa — 200 — 1.0 KiB — 945 ms — h3https://www.ndl.go.jp/api/page/hp/search-news?tag=News&size=6www.ndl.go.jp/api/page/hp/search-ne... https://www.ndl.go.jp/api/page/hp/search-news?tag=News&size=6 — 200 — 4.3 KiB — 718 ms — h3https://www.ndl.go.jp/api/calendar?lib=TML&from=1775001600000&to=1777507200000www.ndl.go.jp/api/calendar?lib=TML&... https://www.ndl.go.jp/api/calendar?lib=TML&from=1775001600000&to=1777507200000 — 200 — 1.2 KiB — 490 ms — h3https://www.ndl.go.jp/api/calendar?lib=KSK&from=1775001600000&to=1777507200000www.ndl.go.jp/api/calendar?lib=KSK&... https://www.ndl.go.jp/api/calendar?lib=KSK&from=1775001600000&to=1777507200000 — 200 — 1.2 KiB — 1.9 s — h3https://www.ndl.go.jp/api/calendar?lib=ILCL&from=1775001600000&to=1777507200000www.ndl.go.jp/api/calendar?lib=ILCL... https://www.ndl.go.jp/api/calendar?lib=ILCL&from=1775001600000&to=1777507200000 — 200 — 1.2 KiB — 486 ms — h3https://www.ndl.go.jp/api/data/retrievewww.ndl.go.jp/api/data/retrieve https://www.ndl.go.jp/api/data/retrieve — 200 — 1.5 KiB — 1.0 s — h3https://www.ndl.go.jp/statistics/ios-v2-prod-statistics/recordwww.ndl.go.jp/statistics/ios-v2-pro... https://www.ndl.go.jp/statistics/ios-v2-prod-statistics/record — 200 — 664 B — 711 ms — h3https://www.ndl.go.jp/_nuxt/DOPaxgQJ.jswww.ndl.go.jp/_nuxt/DOPaxgQJ.js https://www.ndl.go.jp/_nuxt/DOPaxgQJ.js — 200 — 1.8 KiB — 25 ms — h3https://www.ndl.go.jp/_nuxt/_...IqWu5xEg.csswww.ndl.go.jp/_nuxt/_...IqWu5xEg.cs... https://www.ndl.go.jp/_nuxt/_...IqWu5xEg.css — 200 — 1.4 KiB — 25 ms — h3https://www.ndl.go.jp/assets/hp/favicon/favicon.icowww.ndl.go.jp/assets/hp/favicon/fav... https://www.ndl.go.jp/assets/hp/favicon/favicon.ico — 200 — 4.4 KiB — 244 ms — h3
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 2437ms · 1169KB · ¥6/mo
Unattributable
Other
Costly
Execution 963ms
Transfer 0 KB
Monthly Cost ¥2/mo
www.ndl.go.jp
Other
Costly
Execution 898ms
Transfer 1113 KB
Unused 43%
Monthly Cost ¥2/mo
www.ndl.go.jp
Other
Costly
Execution 576ms
Transfer 55 KB
Monthly Cost ¥1/mo

These scripts may cost more than they're worth

  • Unattributable adds 963ms and costs ~¥2/month
  • www.ndl.go.jp adds 898ms and costs ~¥2/month
  • www.ndl.go.jp adds 576ms and costs ~¥1/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

Unattributable takes 963ms 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.ndl.go.jp takes 898ms 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.ndl.go.jp takes 576ms 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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