Performance
· 16 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.
7.28 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
20.00 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
1.84 s
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.002
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
8.83 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.
20.37 s
Page Load Progression
FPage Weight BudgetAction2.8 MB transferred, 114 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
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 CostAction6546ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.zalando.es/KAU4D/3/_I/zTpL/t1eXkK6H/Qr5kcDYruL/FRVseBwNCA/SwxNLR/oQblcq?v=1634f461-b24e-a1f7-1bb9-124115c80211 | 1168ms | 1094ms | 38ms | 3rd |
| https://mosaic01.ztat.net/base-assets/9-1-0/require-2.1.22.min.js | 1022ms | 990ms | 4ms | 3rd |
| Unattributable | 971ms | 230ms | 0ms | 3rd |
| https://mosaic01.ztat.net/base-assets/9-1-0/assets/bundle.js | 793ms | 617ms | 19ms | 3rd |
| https://www.zalando.es/KAU4D/3/_I/zTpL/t1eXkK6H/3z5kcDJQuLr0Nhui/R05geBwNCA/c0VFXW/18TjQB | 653ms | 492ms | 41ms | 3rd |
| https://www.zalando.es/ | 435ms | 31ms | 59ms | 3rd |
| https://mosaic01.ztat.net/pnl/gtag/js?id=G-MDW1S9PQPW&l=dataLayerGA4 | 377ms | 296ms | 43ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-T3W9FX&l=dataLayer | 330ms | 282ms | 34ms | 3rd |
| https://app.usercentrics.eu/browser-ui/3.101.0/index.module.js | 288ms | 210ms | 1ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-1006368194&cx=c>m=4e6550 | 145ms | 107ms | 37ms | 3rd |
Showing top 10 of 14 scripts
FJS BundlesAction43 scripts, 763 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://mosaic03.ztat.net/seo/glados/cbad27c6eaa5e42abf15-main.js | 226 KB | 197 KB (87%) | ✓ | 3rd |
| https://mosaic02.ztat.net/rnd/ng/re-common-chunk/index-252fdc6d1c203653e8bf.js | 173 KB | 121 KB (70%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-T3W9FX&l=dataLayer | 151 KB | 74 KB (49%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-1006368194&cx=c>m=4e6550 | 144 KB | 66 KB (46%) | ✓ | 3rd |
| https://mosaic01.ztat.net/pnl/gtag/js?id=G-MDW1S9PQPW&l=dataLayerGA4 | 171 KB | 62 KB (37%) | ✓ | 3rd |
| https://app.usercentrics.eu/browser-ui/3.101.0/index.module.js | 121 KB | 53 KB (44%) | ✓ | 3rd |
| https://mosaic02.ztat.net/rnd/ng/runtime-concurrent-e8de382cfcdcc9a95fba.js | 158 KB | 48 KB (30%) | ✓ | 3rd |
| https://www.zalando.es/KAU4D/3/_I/zTpL/t1eXkK6H/3z5kcDJQuLr0Nhui/R05geBwNCA/c0VFXW/18TjQB | 181 KB | 39 KB (22%) | ✓ | 3rd |
| https://www.zalando.es/KAU4D/3/_I/zTpL/t1eXkK6H/Qr5kcDYruL/FRVseBwNCA/SwxNLR/oQblcq?v=1634f461-b24e-a1f7-1bb9-124115c80211 | 156 KB | 31 KB (20%) | ✓ | 3rd |
| https://app.usercentrics.eu/browser-ui/3.101.0/VirtualServiceItem-ba2ffbd9.js | 49 KB | 26 KB (54%) | ✓ | 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 InventoryAction114 resources · 2.8 MB · 763 KB savings availableFIX
~762.8 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 114 resources | 2.8 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BImage Optimization24 images, 0 KB saveableREVIEW
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 Loading3 fonts (203 KB)PASS
Web fonts
3
203 KB total
Render-blocking
0
of 3
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 HintsNo optimization neededPASS
Network Waterfall114 requests over 4676msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.zalando.es www.zalando.es | Other | 1168ms | 156 KB | 20% | $16/mo | Costly |
mosaic01.ztat.net mosaic01.ztat.net | Other | 1022ms | 8 KB | — | $14/mo | Costly |
Unattributable Unattributable | Other | 971ms | 0 KB | — | $13/mo | Costly |
mosaic01.ztat.net mosaic01.ztat.net | Other | 793ms | 80 KB | 29% | $11/mo | Costly |
www.zalando.es www.zalando.es | Other | 653ms | 1 KB | 22% | $9/mo | Costly |
www.zalando.es www.zalando.es | Other | 435ms | 99 KB | — | $6/mo | Costly |
mosaic01.ztat.net mosaic01.ztat.net | Other | 377ms | 171 KB | 37% | $5/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 330ms | 151 KB | 49% | $4/mo | Costly |
app.usercentrics.eu app.usercentrics.eu | Other | 288ms | 121 KB | 44% | $4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 145ms | 144 KB | 46% | $2/mo | Optional |
mosaic02.ztat.net mosaic02.ztat.net | Other | 96ms | 158 KB | 30% | $1/mo | Optional |
mosaic03.ztat.net mosaic03.ztat.net | Other | 93ms | 226 KB | 87% | $1/mo | Optional |
www.zalando.es www.zalando.es | Other | 88ms | 9 KB | — | $1/mo | Optional |
mosaic02.ztat.net mosaic02.ztat.net | Other | 87ms | 173 KB | 70% | $1/mo | Optional |
These scripts may cost more than they're worth
- www.zalando.es adds 1168ms and costs ~$16/month
- mosaic01.ztat.net adds 1022ms and costs ~$14/month
- Unattributable adds 971ms and costs ~$13/month
- mosaic01.ztat.net adds 793ms and costs ~$11/month
- www.zalando.es adds 653ms and costs ~$9/month
- www.zalando.es adds 435ms and costs ~$6/month
- mosaic01.ztat.net adds 377ms and costs ~$5/month
- Google Tag Manager adds 330ms and costs ~$4/month
- app.usercentrics.eu adds 288ms and costs ~$4/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.zalando.es takes 1168ms 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
mosaic01.ztat.net takes 1022ms 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 971ms 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
mosaic01.ztat.net takes 793ms 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.zalando.es takes 653ms 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.zalando.es takes 435ms 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
mosaic01.ztat.net takes 377ms 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 330ms 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
app.usercentrics.eu takes 288ms 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
87% of mosaic03.ztat.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
70% of mosaic02.ztat.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
Real-User Performance (CrUX)Field metrics from the Chrome User Experience ReportINFO
Chrome User Experience (CrUX)
Real-user metrics from the Chrome UX Report (2026-04-07 — 2026-05-04)
LCP (p75)
932 ms
97% good
INP (p75)
62 ms
99% good
CLS (p75)
0.000
99% good
FCP (p75)
931 ms
TTFB (p75)
766 ms