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.
1.09 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
1.48 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
374 ms
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.
1.71 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.
5.38 s
Page Load Progression
375 ms 750 ms 1.1 s 1.5 s
1.9 s
2.2 s 2.6 s 3.0 sFPage Weight BudgetAction2.9 MB transferred, 116 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 BundlesAction37 scripts, 659 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtag/js?id=G-CS3DSQ64VQ&cx=c>m=4e64k0 | 164 KB | 64 KB (39%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=DC-14853655&cx=c>m=4e64k0 | 129 KB | 62 KB (48%) | ✓ | 3rd |
| https://analytics.tiktok.com/i18n/pixel/static/main.MWE0ZWQ3ZWQwMQ.js | 110 KB | 62 KB (57%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-12345&cx=c>m=4e64k0 | 137 KB | 61 KB (45%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-970895607&cx=c>m=4e64k0 | 145 KB | 60 KB (42%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-794194365&cx=c>m=4e64k0 | 134 KB | 59 KB (44%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-976087125&cx=c>m=4e64k0 | 136 KB | 59 KB (43%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-990532474&cx=c>m=4e64k0 | 134 KB | 58 KB (43%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-TDHW9DQ | 181 KB | 57 KB (32%) | ✓ | 3rd |
| https://cdn-4.convertexperiments.com/v1/js/10042695-10043546.js?environment=production | 86 KB | 45 KB (52%) | ✓ | 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 InventoryAction116 resources · 2.9 MB · 659 KB savings availableFIX
~659.4 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 116 resources | 2.9 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction29 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
CJS Execution CostAction1689ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| Unattributable | 286ms | 10ms | 0ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-TDHW9DQ | 208ms | 173ms | 31ms | 3rd |
| https://cdn-4.convertexperiments.com/v1/js/10042695-10043546.js?environment=production | 132ms | 118ms | 8ms | 3rd |
| https://www.rijksmuseum.nl/statics/generated/vue-router.1d374ba6a02c7388ebe5.mjs | 129ms | 108ms | 1ms | 3rd |
| https://www.rijksmuseum.nl/nl | 122ms | 4ms | 2ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-12345&cx=c>m=4e64k0 | 104ms | 84ms | 18ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-CS3DSQ64VQ&cx=c>m=4e64k0 | 93ms | 79ms | 12ms | 3rd |
| https://script.hotjar.com/modules.6a0f3932cb1341a35c18.js | 87ms | 75ms | 10ms | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-990532474&cx=c>m=4e64k0 | 84ms | 57ms | 8ms | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-976087125&cx=c>m=4e64k0 | 82ms | 70ms | 10ms | 3rd |
Showing top 10 of 15 scripts
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 Loading2 fonts (31 KB)PASS
Web fonts
2
31 KB total
Render-blocking
0
of 2
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 Waterfall116 requests over 4132msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
Unattributable Unattributable | Other | 286ms | 0 KB | — | €3/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 208ms | 181 KB | 32% | €2/mo | Costly |
cdn-4.convertexperiments.com cdn-4.convertexperiments.com | Other | 132ms | 86 KB | 52% | €1/mo | Optional |
www.rijksmuseum.nl www.rijksmuseum.nl | Other | 129ms | 10 KB | — | €1/mo | Optional |
www.rijksmuseum.nl www.rijksmuseum.nl | Other | 122ms | 109 KB | — | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 104ms | 137 KB | 45% | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 93ms | 164 KB | 39% | €1/mo | Optional |
Hotjar script.hotjar.com | Session Replay | 87ms | 57 KB | 67% | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 84ms | 134 KB | 43% | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 82ms | 136 KB | 43% | €1/mo | Optional |
analytics.tiktok.com analytics.tiktok.com | Other | 79ms | 110 KB | 57% | €1/mo | Optional |
Microsoft Clarity scripts.clarity.ms | Session Replay | 78ms | 25 KB | — | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 72ms | 145 KB | 42% | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 69ms | 134 KB | 44% | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 64ms | 129 KB | 48% | €1/mo | Optional |
These scripts may cost more than they're worth
- Unattributable adds 286ms and costs ~€3/month
- Google Tag Manager adds 208ms and costs ~€2/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
Unattributable takes 286ms 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 208ms 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
52% of cdn-4.convertexperiments.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
67% of Hotjar'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
57% of analytics.tiktok.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