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.
3.52 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
7.66 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
2.80 s
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.000
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
7.66 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.
20.78 s
Page Load Progression
834 ms
1.7 s 2.5 s 3.3 s
4.2 s 5.0 s
5.8 s
6.7 sFPage Weight BudgetAction3.3 MB transferred, 157 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
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 CostAction14352ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://assets.services.prod.kratos.zappos.com/kratos-assets/_next/static/chunks/8315-e5d0b0f7b97f9546.js | 5931ms | 4055ms | 22ms | 3rd |
| https://www.zappos.com/ | 2415ms | 166ms | 197ms | 3rd |
| Unattributable | 2040ms | 110ms | 0ms | 3rd |
| https://assets.services.prod.kratos.zappos.com/kratos-assets/_next/static/chunks/2401-dcf64d72e0367e5a.js | 566ms | 557ms | 6ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-M3HN5KQH | 478ms | 381ms | 63ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-8VWCJY5CWM&cx=c>m=4e64k0 | 471ms | 408ms | 56ms | 3rd |
| https://js.stripe.com/clover/stripe.js | 380ms | 242ms | 136ms | 3rd |
| https://connect.facebook.net/en_US/fbevents.js | 369ms | 328ms | 38ms | 3rd |
| https://assets.services.prod.kratos.zappos.com/kratos-assets/_next/static/chunks/87c73c54-2ddfe8b2f2752ebb.js | 322ms | 263ms | 19ms | 3rd |
| https://cdn.amplitude.com/libs/analytics-browser-gtm-wrapper-3.15.0.js.br | 271ms | 212ms | 53ms | 3rd |
Showing top 10 of 20 scripts
FJS BundlesAction75 scripts, 516 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://js.stripe.com/clover/stripe.js | 225 KB | 163 KB (73%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-8VWCJY5CWM&cx=c>m=4e64k0 | 165 KB | 64 KB (39%) | ✓ | 3rd |
| https://cdn.amplitude.com/libs/analytics-browser-gtm-wrapper-3.15.0.js.br | 74 KB | 57 KB (77%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-M3HN5KQH | 147 KB | 56 KB (38%) | ✓ | 3rd |
| https://assets.services.prod.kratos.zappos.com/kratos-assets/_next/static/chunks/3769-2c1f1d1de825d91c.js | 70 KB | 52 KB (80%) | ✓ | 3rd |
| https://assets.services.prod.kratos.zappos.com/kratos-assets/_next/static/chunks/3615-8e1b56a65e247c87.js | 74 KB | 36 KB (51%) | ✓ | 3rd |
| https://connect.facebook.net/en_US/fbevents.js | 97 KB | 33 KB (34%) | ✓ | 3rd |
| https://assets.services.prod.kratos.zappos.com/kratos-assets/_next/static/chunks/2382-bf835854fcb2264b.js | 46 KB | 30 KB (65%) | ✓ | 3rd |
| https://cdn.amplitude.com/script/8b91e3eff649558ed402aa2538381888.experiment.js | 44 KB | 24 KB (56%) | ✓ | 3rd |
| https://assets.services.prod.kratos.zappos.com/kratos-assets/_next/static/chunks/1822-f39750b5afa30b93.js | 9 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
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 InventoryAction157 resources · 3.3 MB · 516 KB savings availableFIX
~515.6 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 157 resources | 3.3 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction27 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.
Performance issues directly impact user engagement and conversion rates.
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 Loading5 fonts (191 KB)PASS
Web fonts
5
191 KB total
Render-blocking
0
of 5
Dominant font-display
swap
Most common across fonts
Font loading timeline
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)
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource Hints7 hints, 0 missing preconnectsPASS
Current Resource Hints
7 resource hints configured
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
A+Third-Party ResourcesNo third-party resources detectedPASS
Network Waterfall157 requests over 4449msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
assets.services.prod.kratos.zappos.com assets.services.prod.kratos.zappos.com | Other | 5931ms | 46 KB | — | $34/mo | Costly |
www.zappos.com www.zappos.com | Other | 2415ms | 182 KB | — | $14/mo | Costly |
Unattributable Unattributable | Other | 2040ms | 0 KB | — | $12/mo | Costly |
assets.services.prod.kratos.zappos.com assets.services.prod.kratos.zappos.com | Other | 566ms | 20 KB | — | $3/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 478ms | 147 KB | 38% | $3/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 471ms | 165 KB | 39% | $3/mo | Costly |
Stripe js.stripe.com | Payment | 380ms | 225 KB | 73% | $2/mo | Essential |
Facebook Pixel connect.facebook.net | Advertising | 369ms | 97 KB | 34% | $2/mo | Costly |
assets.services.prod.kratos.zappos.com assets.services.prod.kratos.zappos.com | Other | 322ms | 53 KB | — | $2/mo | Costly |
Amplitude cdn.amplitude.com | Analytics | 271ms | 74 KB | 77% | $2/mo | Costly |
Facebook Pixel connect.facebook.net | Advertising | 227ms | 45 KB | — | $1/mo | Costly |
dynamic.criteo.com dynamic.criteo.com | Other | 181ms | 25 KB | — | $1/mo | Optional |
sc-static.net sc-static.net | Other | 130ms | 25 KB | — | $1/mo | Optional |
Bing UET bat.bing.com | Advertising | 113ms | 15 KB | — | $1/mo | Optional |
Amplitude cdn.amplitude.com | Analytics | 89ms | 44 KB | 56% | $1/mo | Optional |
tr.snapchat.com tr.snapchat.com | Other | 88ms | 0 KB | — | $0/mo | Optional |
cdn.id5-sync.com cdn.id5-sync.com | Other | 87ms | 34 KB | — | $0/mo | Optional |
Amplitude cdn.amplitude.com | Analytics | 70ms | 35 KB | — | $0/mo | Optional |
assets.services.prod.kratos.zappos.com assets.services.prod.kratos.zappos.com | Other | 70ms | 20 KB | — | $0/mo | Optional |
www.zappos.com www.zappos.com | Other | 54ms | 1 KB | — | $0/mo | Optional |
These scripts may cost more than they're worth
- assets.services.prod.kratos.zappos.com adds 5931ms and costs ~$34/month
- www.zappos.com adds 2415ms and costs ~$14/month
- Unattributable adds 2040ms and costs ~$12/month
- assets.services.prod.kratos.zappos.com adds 566ms and costs ~$3/month
- Google Tag Manager adds 478ms and costs ~$3/month
- Google Tag Manager adds 471ms and costs ~$3/month
- Facebook Pixel adds 369ms and costs ~$2/month
- assets.services.prod.kratos.zappos.com adds 322ms and costs ~$2/month
- Amplitude adds 271ms and costs ~$2/month
- Facebook Pixel adds 227ms and costs ~$1/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
assets.services.prod.kratos.zappos.com takes 5931ms 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.zappos.com takes 2415ms 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 2040ms 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
assets.services.prod.kratos.zappos.com takes 566ms 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
Google Tag Manager takes 478ms 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
Google Tag Manager takes 471ms 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
73% of Stripe'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
Facebook Pixel takes 369ms 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
assets.services.prod.kratos.zappos.com takes 322ms 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
Amplitude takes 271ms 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
77% of Amplitude'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
Facebook Pixel takes 227ms 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
56% of Amplitude'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