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
40 images, 0 KB saveable
REVIEW
40 images, 0 KB saveable
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/icon-ca... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/common/img-t... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/img-her... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/img-abo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://ui-storage.userlocal.jp/public/cta/54089/1... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/common/img-d... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/column/wp-content/uploads/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/common/logo.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/img-her... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/event-s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/img-abo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/icon-st... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/common/img-s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/icon-ad... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/column/wp-content/uploads/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/img-abo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/icon-pl... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/common/icons... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/column/wp-content/uploads/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/illust-... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/img-abo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/img-her... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/common/icons... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://rs.sakura.ad.jp/assets/images/home/event-s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
40images771 KB
0oversized-0 KB
23legacy format
25missing dimensionsCLS 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
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
Set explicit width and height to prevent CLS.
Why this matters
Performance issues directly impact user engagement and conversion rates.
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
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
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 (1228 KB)
PASS
1 fonts (1228 KB)
Info::
i
1 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
1
1228 KB total
Render-blocking
0
of 1
Dominant font-display
swap
Most common across fonts
Font loading timeline
TransferFOIT (block)FOUT (swap)
NotoSansJP-VariableFont...woff2swap
Size1228 KB
Load time1.9 s
Start2.3 s
RiskFOUT — 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 ~614 KB and ~1228 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
2 hints, 0 missing preconnects
PASS
2 hints, 0 missing preconnects
Info::
✓
Page uses 2 resource hint(s)
Current Resource Hints
preconnect
2
preload—
dns-prefetch—
prefetch—
2 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
119 requests over 7051ms
INFO
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-party5998ms · 1338KB · ¥36/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
rs.sakura.ad.jp
rs.sakura.ad.jp
Other
1660ms
10 KB
—
¥10/mo
Costly
Unattributable
Unattributable
Other
1066ms
0 KB
—
¥6/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
735ms
188 KB
28%
¥4/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
362ms
179 KB
38%
¥2/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
347ms
146 KB
42%
¥2/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
312ms
143 KB
43%
¥2/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
279ms
176 KB
40%
¥2/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
263ms
172 KB
40%
¥2/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
256ms
160 KB
40%
¥2/mo
Costly
rs.sakura.ad.jp
rs.sakura.ad.jp
Other
203ms
3 KB
—
¥1/mo
Costly
Facebook Pixel
connect.facebook.net
Advertising
168ms
97 KB
35%
¥1/mo
Optional
rs.sakura.ad.jp
rs.sakura.ad.jp
Other
149ms
3 KB
—
¥1/mo
Optional
Facebook Pixel
connect.facebook.net
Advertising
139ms
44 KB
—
¥1/mo
Optional
Facebook Pixel
connect.facebook.net
Advertising
60ms
16 KB
—
¥0/mo
Optional
rs.sakura.ad.jp
Other
Costly
Execution1660ms
Transfer10 KB
Monthly Cost¥10/mo
Unattributable
Other
Costly
Execution1066ms
Transfer0 KB
Monthly Cost¥6/mo
Google Tag Manager
Tag Manager
Costly
Execution735ms
Transfer188 KB
Unused28%
Monthly Cost¥4/mo
Google Tag Manager
Tag Manager
Costly
Execution362ms
Transfer179 KB
Unused38%
Monthly Cost¥2/mo
Google Tag Manager
Tag Manager
Costly
Execution347ms
Transfer146 KB
Unused42%
Monthly Cost¥2/mo
Google Tag Manager
Tag Manager
Costly
Execution312ms
Transfer143 KB
Unused43%
Monthly Cost¥2/mo
Google Tag Manager
Tag Manager
Costly
Execution279ms
Transfer176 KB
Unused40%
Monthly Cost¥2/mo
Google Tag Manager
Tag Manager
Costly
Execution263ms
Transfer172 KB
Unused40%
Monthly Cost¥2/mo
Google Tag Manager
Tag Manager
Costly
Execution256ms
Transfer160 KB
Unused40%
Monthly Cost¥2/mo
rs.sakura.ad.jp
Other
Costly
Execution203ms
Transfer3 KB
Monthly Cost¥1/mo
Facebook Pixel
Advertising
Optional
Execution168ms
Transfer97 KB
Unused35%
Monthly Cost¥1/mo
rs.sakura.ad.jp
Other
Optional
Execution149ms
Transfer3 KB
Monthly Cost¥1/mo
Facebook Pixel
Advertising
Optional
Execution139ms
Transfer44 KB
Monthly Cost¥1/mo
Facebook Pixel
Advertising
Optional
Execution60ms
Transfer16 KB
Monthly Cost¥0/mo
These scripts may cost more than they're worth
rs.sakura.ad.jp adds 1660ms and costs ~¥10/month
Unattributable adds 1066ms and costs ~¥6/month
Google Tag Manager adds 735ms and costs ~¥4/month
Google Tag Manager adds 362ms and costs ~¥2/month
Google Tag Manager adds 347ms and costs ~¥2/month
Google Tag Manager adds 312ms and costs ~¥2/month
Google Tag Manager adds 279ms and costs ~¥2/month
Google Tag Manager adds 263ms and costs ~¥2/month
Google Tag Manager adds 256ms and costs ~¥2/month
rs.sakura.ad.jp adds 203ms 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
rs.sakura.ad.jp takes 1660ms 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 1066ms 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
Google Tag Manager takes 735ms 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
Google Tag Manager takes 362ms 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
Google Tag Manager takes 347ms 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
Google Tag Manager takes 312ms 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
Google Tag Manager takes 279ms 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
Google Tag Manager takes 263ms 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
Google Tag Manager takes 256ms 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
rs.sakura.ad.jp takes 203ms 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.