Performance
· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.Performance-focused optimization plan with CWV assessment, top offenders, and time estimates
First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.
887 ms
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
3.67 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
0 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.067
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
1.00 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.
3.68 s
Page Load Progression
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
DPage Weight InventoryAction99 resources · 1.8 MB · 152 KB savings availableFIX
~151.6 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 99 resources | 1.8 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CPage Weight BudgetAction1.8 MB transferred, 99 requestsREVIEW
Subset fonts to include only used characters, or switch to system font stacks.
Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).
Source: web.dev font loading
CImage OptimizationAction30 images, 0 KB saveableREVIEW
Set explicit width and height to prevent CLS.
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.
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.
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.
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.
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.
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.
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
BJS Execution Cost541ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.kyoto-u.ac.jp/ja | 305ms | 1ms | 0ms | 3rd |
| Unattributable | 118ms | 21ms | 0ms | 3rd |
| https://www.kyoto-u.ac.jp/sites/default/files/js/js_3wLlTtZB4ydNzDsfU_DCRct5H0cMVEMK90fneOskkE8.js?scope=footer&delta=1&language=ja&theme=camphor&include=eJxdzEEOwjAMRNELufWRkEksx8hpqthQwumBqgLB5kvzFpOorqV1zGOhqmkqTJk7pIPF2pls8himi3zYTTN7aRtIa2J8ChKUV_73TBe6_2IFo8fAd8CDQj00OeZ-Xcnmr8BNeXPcu988ATcxQl0 | 118ms | 31ms | 3ms | 3rd |
CJS BundlesAction8 scripts, 152 KB unusedREVIEW
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtag/js?id=G-P51JW1MC7Y&cx=c>m=4e64h1 | 154 KB | 64 KB (41%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-PVPH2PW | 117 KB | 63 KB (54%) | ✓ | 3rd |
| https://www.kyoto-u.ac.jp/sites/default/files/js/js_3wLlTtZB4ydNzDsfU_DCRct5H0cMVEMK90fneOskkE8.js?scope=footer&delta=1&language=ja&theme=camphor&include=eJxdzEEOwjAMRNELufWRkEksx8hpqthQwumBqgLB5kvzFpOorqV1zGOhqmkqTJk7pIPF2pls8himi3zYTTN7aRtIa2J8ChKUV_73TBe6_2IFo8fAd8CDQj00OeZ-Xcnmr8BNeXPcu988ATcxQl0 | 43 KB | 25 KB (58%) | ✓ | 3rd |
| https://www.kyoto-u.ac.jp/sites/default/files/js/js_nLEIK4XX99YtlyCTslopx58sCv5mvfcCH4DM7PQ_APo.js?scope=header&delta=0&language=ja&theme=camphor&include=eJxdzEEOwjAMRNELufWRkEksx8hpqthQwumBqgLB5kvzFpOorqV1zGOhqmkqTJk7pIPF2pls8himi3zYTTN7aRtIa2J8ChKUV_73TBe6_2IFo8fAd8CDQj00OeZ-Xcnmr8BNeXPcu988ATcxQl0 | 0 KB | — | ✓ | 3rd |
| https://www.kyoto-u.ac.jp/modules/contrib/google_tag/js/gtag.js?tcr8t9 | 1 KB | — | ✓ | 3rd |
| https://www.kyoto-u.ac.jp/modules/contrib/google_tag/js/gtm.js?tcr8t9 | 1 KB | — | ✓ | 3rd |
| https://www.kyoto-u.ac.jp/core/assets/vendor/jquery/jquery.min.js?v=4.0.0-rc.1 | 32 KB | — | ✓ | 3rd |
| https://www.kyoto-u.ac.jp/libraries/lazysizes/lazysizes.min.js | 4 KB | — | ✓ | 3rd |
Consider code splitting or tree shaking to reduce unused code.
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.
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.
This bundle has high unused code — code-split or tree-shake to ship only what executes.
Source: web.dev / Lighthouse coverage
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
No green hosting detected
A+Text CompressionAll text resources are compressedPASS
A+Font Loading45 fonts (1045 KB)PASS
Web fonts
45
1045 KB total
Render-blocking
0
of 45
Dominant font-display
swap
Most common across fonts
Font loading timeline
- 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 ~63 KB and ~126 ms
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
Network Waterfall99 requests over 1958msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.kyoto-u.ac.jp www.kyoto-u.ac.jp | Other | 305ms | 24 KB | — | ¥421/mo | Costly |
Unattributable Unattributable | Other | 118ms | 0 KB | — | ¥163/mo | Costly |
www.kyoto-u.ac.jp www.kyoto-u.ac.jp | Other | 118ms | 43 KB | 58% | ¥163/mo | Costly |
These scripts may cost more than they're worth
- www.kyoto-u.ac.jp adds 305ms and costs ~¥421/month
- Unattributable adds 118ms and costs ~¥163/month
- www.kyoto-u.ac.jp adds 118ms and costs ~¥163/month
100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.
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
www.kyoto-u.ac.jp takes 305ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
Unattributable takes 118ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
www.kyoto-u.ac.jp takes 118ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
58% of www.kyoto-u.ac.jp's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev