Performance
· 17 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.
2.53 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
18.31 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
7.57 s
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.139
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
14.69 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.
39.94 s
Page Load Progression
797 ms 1.6 s
2.4 s 3.2 s
4.0 s 4.8 s 5.6 s
6.4 sFPage Weight BudgetAction7.7 MB transferred, 297 requestsFIX
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.
Source: web.dev
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.
Source: web.dev
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
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.
Source: web.dev
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
FJS Execution CostAction26978ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://u-web-assets.mercdn.net/builds/r-v1.26.1585/_next/static/chunks/framework-410df72d408e49c5.js | 7336ms | 6578ms | 22ms | 3rd |
| https://u-web-assets.mercdn.net/builds/r-v1.26.1585/_next/static/chunks/pages/_app-951ae3cec2930a6d.js | 6936ms | 4630ms | 302ms | 3rd |
| Unattributable | 4003ms | 312ms | 0ms | 3rd |
| https://cdn.quadpay.com/v1/quadpay.js | 1175ms | 819ms | 98ms | 3rd |
| https://www.mercari.com/ | 1035ms | 43ms | 5ms | 3rd |
| https://u-web-assets.mercdn.net/builds/r-v1.26.1585/_next/static/chunks/28114-4e311b2e1d59c295.js | 518ms | 434ms | 3ms | 3rd |
| https://www.mercari.com/ko40/?id=G-DJ5N7E6D07&cx=c>m=4e64k1 | 446ms | 385ms | 55ms | 3rd |
| https://www.mercari.com/ko40/?id=AW-880627815&cx=c>m=4e64k1 | 427ms | 360ms | 60ms | 3rd |
| https://www.mercari.com/cdn-cgi/challenge-platform/scripts/jsd/main.js | 424ms | 408ms | 3ms | 3rd |
| https://www.mercari.com/ko40/?id=AW-782098151&cx=c>m=4e64k1 | 389ms | 337ms | 48ms | 3rd |
Showing top 10 of 30 scripts
FJS BundlesAction70 scripts, 1.8 MB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://u-web-assets.mercdn.net/builds/r-v1.26.1585/_next/static/chunks/pages/_app-951ae3cec2930a6d.js | 650 KB | 286 KB (44%) | ✓ | 3rd |
| https://www.gstatic.com/recaptcha/releases/gTpTIWhbKpxADzTzkcabhXN4/recaptcha__en.js | 0 KB | 177 KB (49%) | ✓ | 3rd |
| https://www.gstatic.com/recaptcha/releases/gTpTIWhbKpxADzTzkcabhXN4/recaptcha__en.js | 362 KB | 177 KB (49%) | ✓ | 3rd |
| https://www.gstatic.com/recaptcha/releases/gTpTIWhbKpxADzTzkcabhXN4/recaptcha__en.js | 362 KB | 177 KB (49%) | ✓ | 3rd |
| https://cdn.quadpay.com/v1/quadpay.js | 202 KB | 130 KB (65%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-MSDTXHX | 167 KB | 109 KB (65%) | ✓ | 3rd |
| https://www.mercari.com/ko40/gtd?id=AW-dynamic_home&cx=c>m=4e64k1 | 140 KB | 84 KB (60%) | ✓ | 3rd |
| https://www.mercari.com/ko40/?id=G-DJ5N7E6D07&cx=c>m=4e64k1 | 177 KB | 73 KB (41%) | ✓ | 3rd |
| https://www.mercari.com/ko40/ | 175 KB | 71 KB (40%) | ✓ | 3rd |
| https://accounts.google.com/gsi/client | 96 KB | 68 KB (71%) | ✓ | 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
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
FPage Weight InventoryAction297 resources · 7.7 MB · 1.8 MB savings availableFIX
~1.8 MiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 297 resources | 7.7 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction159 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
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
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
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
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
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
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
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 Loading8 fonts (405 KB)PASS
Web fonts
8
405 KB total
Render-blocking
0
of 8
Dominant font-display
swap
Most common across fonts
Font loading timeline
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
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 ~86 KB and ~172 ms
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
A+Third-Party ResourcesNo third-party resources detectedPASS
Network Waterfall297 requests over 14124msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
u-web-assets.mercdn.net u-web-assets.mercdn.net | Other | 7336ms | 57 KB | — | $97/mo | Costly |
u-web-assets.mercdn.net u-web-assets.mercdn.net | Other | 6936ms | 650 KB | 44% | $92/mo | Costly |
Unattributable Unattributable | Other | 4003ms | 0 KB | — | $53/mo | Costly |
cdn.quadpay.com cdn.quadpay.com | Other | 1175ms | 202 KB | 65% | $16/mo | Costly |
www.mercari.com www.mercari.com | Other | 1035ms | 3 KB | — | $14/mo | Costly |
u-web-assets.mercdn.net u-web-assets.mercdn.net | Other | 518ms | 2 KB | — | $7/mo | Costly |
www.mercari.com www.mercari.com | Other | 446ms | 177 KB | 41% | $6/mo | Costly |
www.mercari.com www.mercari.com | Other | 427ms | 150 KB | 41% | $6/mo | Costly |
www.mercari.com www.mercari.com | Other | 424ms | 0 KB | — | $6/mo | Costly |
www.mercari.com www.mercari.com | Other | 389ms | 150 KB | 42% | $5/mo | Costly |
u-web-assets.mercdn.net u-web-assets.mercdn.net | Other | 384ms | 61 KB | 42% | $5/mo | Costly |
www.gstatic.com www.gstatic.com | Other | 363ms | 0 KB | 49% | $5/mo | Costly |
u-web-assets.mercdn.net u-web-assets.mercdn.net | Other | 348ms | 5 KB | — | $5/mo | Costly |
www.mercari.com www.mercari.com | Other | 342ms | 136 KB | 49% | $5/mo | Costly |
www.mercari.com www.mercari.com | Other | 333ms | 175 KB | 40% | $4/mo | Costly |
www.mercari.com www.mercari.com | Other | 332ms | 143 KB | 46% | $4/mo | Costly |
www.mercari.com www.mercari.com | Other | 325ms | 135 KB | 49% | $4/mo | Costly |
www.mercari.com www.mercari.com | Other | 257ms | 135 KB | 49% | $3/mo | Costly |
u-web-assets.mercdn.net u-web-assets.mercdn.net | Other | 196ms | 2 KB | — | $3/mo | Optional |
Facebook Pixel connect.facebook.net | Advertising | 192ms | 97 KB | 35% | $3/mo | Optional |
www.mercari.com www.mercari.com | Other | 188ms | 140 KB | 60% | $2/mo | Optional |
Facebook Pixel connect.facebook.net | Advertising | 187ms | 45 KB | — | $2/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 176ms | 167 KB | 65% | $2/mo | Optional |
u-web-assets.mercdn.net u-web-assets.mercdn.net | Other | 142ms | 42 KB | 52% | $2/mo | Optional |
u-web-assets.mercdn.net u-web-assets.mercdn.net | Other | 125ms | 8 KB | — | $2/mo | Optional |
consent.trustarc.com consent.trustarc.com | Other | 103ms | 36 KB | 61% | $1/mo | Optional |
consent.trustarc.com consent.trustarc.com | Other | 97ms | 2 KB | — | $1/mo | Optional |
consent.trustarc.com consent.trustarc.com | Other | 82ms | 2 KB | — | $1/mo | Optional |
accounts.google.com accounts.google.com | Other | 65ms | 96 KB | 71% | $1/mo | Optional |
consent.trustarc.com consent.trustarc.com | Other | 54ms | 13 KB | — | $1/mo | Optional |
These scripts may cost more than they're worth
- u-web-assets.mercdn.net adds 7336ms and costs ~$97/month
- u-web-assets.mercdn.net adds 6936ms and costs ~$92/month
- Unattributable adds 4003ms and costs ~$53/month
- cdn.quadpay.com adds 1175ms and costs ~$16/month
- www.mercari.com adds 1035ms and costs ~$14/month
- u-web-assets.mercdn.net adds 518ms and costs ~$7/month
- www.mercari.com adds 446ms and costs ~$6/month
- www.mercari.com adds 427ms and costs ~$6/month
- www.mercari.com adds 424ms and costs ~$6/month
- www.mercari.com adds 389ms and costs ~$5/month
- u-web-assets.mercdn.net adds 384ms and costs ~$5/month
- www.gstatic.com adds 363ms and costs ~$5/month
- u-web-assets.mercdn.net adds 348ms and costs ~$5/month
- www.mercari.com adds 342ms and costs ~$5/month
- www.mercari.com adds 333ms and costs ~$4/month
- www.mercari.com adds 332ms and costs ~$4/month
- www.mercari.com adds 325ms and costs ~$4/month
- www.mercari.com adds 257ms and costs ~$3/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
u-web-assets.mercdn.net takes 7336ms 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
u-web-assets.mercdn.net takes 6936ms 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 4003ms 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
cdn.quadpay.com takes 1175ms 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
65% of cdn.quadpay.com'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
www.mercari.com takes 1035ms 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
u-web-assets.mercdn.net takes 518ms 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.mercari.com takes 446ms 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.mercari.com takes 427ms 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.mercari.com takes 424ms 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.mercari.com takes 389ms 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
u-web-assets.mercdn.net takes 384ms 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.gstatic.com takes 363ms 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
u-web-assets.mercdn.net takes 348ms 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.mercari.com takes 342ms 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.mercari.com takes 333ms 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.mercari.com takes 332ms 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.mercari.com takes 325ms 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.mercari.com takes 257ms 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
60% of www.mercari.com'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
65% of Google Tag Manager'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
52% of u-web-assets.mercdn.net'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
61% of consent.trustarc.com'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
71% of accounts.google.com'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