Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.

SCORE

GRADE

FIX

REVIEW

PASS

INFO

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop

Performance

100

Accessibility

Best Practices

100

SEO

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

3.21 s

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

3.69 s

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

3.26 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.

6.41 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.

21.95 s

Page Load Progression

486 ms

973 ms

1.5 s

1.9 s

2.4 s

2.9 s

3.4 s

3.9 s

Checks

7 PASS 2 REVIEW 6 FIX

Page Weight Budget

Action

2.9 MB transferred, 115 requests

FIX

2.9 MB transferred, 115 requests

Page weighs 6.9 MB (2.9 MB transferred)

JavaScript is 1.7 MB — consider code splitting or lazy loading

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Got: 1.7 MB

115 HTTP requests — consider bundling or reducing

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Estimated 0.61 g CO2 per page load

2.9 MB transferred

115 requests

0.61 g CO2 per page load

JavaScript 1.7 MiB 61%

Images 982.7 KiB 33%

HTML 113.3 KiB 4%

Fonts 30.5 KiB 1%

CSS 22.5 KiB 1%

Other 7.4 KiB 0%

Other 7.2 KiB 0%

Other 2.9 KiB 0%

Other 1.3 KiB 0%

Other 1.2 KiB 0%

0 2.4 MB 4.9 MB

Over budget

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Why this matters

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.

Why this matters

High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.

Source: web.dev

Third-Party Impact

Action

100% third-party, 0 ms blocking

FIX

100% third-party, 0 ms blocking

Third-party code accounts for 100% of page weight (2.9 MiB of 2.9 MiB)

Third-party blocking time is low (0 ms)

100%

First-party Third-party

JS Execution Cost

Action

7337ms total JS execution

FIX

7337ms total JS execution

Unattributable: 1219ms CPU time

https://www.googletagmanager.com/gtm.js?id=GTM-TDH...: 764ms CPU time

https://www.googletagmanager.com/gtag/js?id=G-CS3D...: 570ms CPU time

https://www.rijksmuseum.nl/nl: 476ms CPU time

https://cdn-4.convertexperiments.com/v1/js/1004269...: 440ms CPU time

Third-party scripts: 7337ms (100% of total)

Main Thread Breakdown

Script Evaluation 64% Other 19% Script Parsing & Compilation 9%

Script	Total	Scripting	Parse/Compile	Party
Unattributable	1219ms	84ms	0ms	3rd
https://www.googletagmanager.com/gtm.js?id=GTM-TDHW9DQ	764ms	658ms	88ms	3rd
https://www.googletagmanager.com/gtag/js?id=G-CS3DSQ64VQ&cx=c&gtm=4e64k0	570ms	454ms	52ms	3rd
https://www.rijksmuseum.nl/nl	476ms	19ms	4ms	3rd
https://cdn-4.convertexperiments.com/v1/js/10042695-10043546.js?environment=production	440ms	363ms	40ms	3rd
https://www.googletagmanager.com/gtag/js?id=G-12345&cx=c&gtm=4e64k0	369ms	296ms	68ms	3rd
https://www.rijksmuseum.nl/statics/generated/vue-router.1d374ba6a02c7388ebe5.mjs	364ms	326ms	5ms	3rd
https://scripts.clarity.ms/0.8.60-beta/clarity.js	346ms	297ms	16ms	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-970895607&cx=c&gtm=4e64k0	323ms	281ms	39ms	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-976087125&cx=c&gtm=4e64k0	302ms	216ms	35ms	3rd

Showing top 10 of 21 scripts

JS Bundles

Action

36 scripts, 650 KB unused

FIX

36 scripts, 650 KB unused

https://www.googletagmanager.com/gtag/js?id=G-CS3D...: 64 KB unused (39%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtag/destination?...: 62 KB unused (48%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtag/js?id=G-1234...: 60 KB unused (44%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtag/destination?...: 60 KB unused (42%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtag/destination?...: 59 KB unused (44%)

Consider code splitting or tree shaking to reduce unused code.

Total unused JavaScript: 650 KB

650 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://www.googletagmanager.com/gtag/js?id=G-CS3DSQ64VQ&cx=c&gtm=4e64k0	164 KB	64 KB (39%)	✓	3rd
https://www.googletagmanager.com/gtag/destination?id=DC-14853655&cx=c&gtm=4e64k0	129 KB	62 KB (48%)	✓	3rd
https://www.googletagmanager.com/gtag/js?id=G-12345&cx=c&gtm=4e64k0	137 KB	60 KB (44%)	✓	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-970895607&cx=c&gtm=4e64k0	145 KB	60 KB (42%)	✓	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-990532474&cx=c&gtm=4e64k0	134 KB	59 KB (44%)	✓	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-794194365&cx=c&gtm=4e64k0	134 KB	59 KB (44%)	✓	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-976087125&cx=c&gtm=4e64k0	136 KB	59 KB (43%)	✓	3rd
https://www.googletagmanager.com/gtm.js?id=GTM-TDHW9DQ	181 KB	57 KB (32%)	✓	3rd
https://analytics.tiktok.com/i18n/pixel/static/main.MWE0ZWQ3ZWQwMQ.js	110 KB	53 KB (57%)	✓	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.

Why this matters

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.

Why this matters

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.

Why this matters

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.

Why this matters

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.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Page Weight Inventory

Action

115 resources · 2.9 MB · 650 KB savings available

FIX

115 resources · 2.9 MB · 650 KB savings available

Page weight 1.9 MB over 1MB target

Got: 2.9 MB Expected: ≤ 1 MB

~650 KB of savings available

114 third-party resources (100% of weight)

1 resources over 200KB

115 resources · 2.9 MiB · 114 third-party 1.9 MiB over 1MB target

JavaScript 61% · 1.7 MiB

Image 33% · 990.4 KiB

Document 4% · 113.4 KiB

Font 1% · 30.5 KiB

CSS 1% · 22.5 KiB

Other 0% · 12.2 KiB

~650.2 KiB of savings available

Remove unused JavaScript: 650.2 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

115 resources			2.9 MiB

HTTP Caching

Action

No cache headers

FIX

No cache headers

No Cache-Control header found

Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

Image Optimization

Action

29 images, 0 KB saveable

REVIEW

29 images, 0 KB saveable

https://www.rijksmuseum.nl/statics/logos/ing.svg is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://www.rijksmuseum.nl/statics/logos/m-ocw-nl.... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://www.rijksmuseum.nl/statics/logos/vrienden-... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://www.rijksmuseum.nl/statics/logos/kpn-logo-... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://www.rijksmuseum.nl/statics/logos/anbi.svg is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

29 images 983 KB

0 oversized -0 KB

27 legacy format

5 missing dimensions CLS risk

Set explicit width and height to prevent CLS.

Why this matters

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.

Why this matters

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.

Why this matters

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.

Why this matters

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.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Green Hosting

Action

Whether the site is served from green-energy infrastructure

REVIEW

Green Hosting

No green hosting detected

A+

Text Compression

All text resources are compressed

PASS

All text resources are compressed

All text resources are properly compressed.

A+

Font Loading

2 fonts (31 KB)

PASS

2 fonts (31 KB)

2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

31 KB total

Render-blocking

of 2

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

Rijksmuseum-Normal.woff2 woff2 swap

Size 15 KB

Load time 138 ms

Start 2.4 s

Risk FOUT — text flashes from fallback to web font

Rijksmuseum-Bold.woff2 woff2 swap

Size 15 KB

Load time 136 ms

Start 2.4 s

Risk FOUT — text flashes from fallback to web font

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 Caching

All resources properly cached

PASS

All resources properly cached

No caching issues found

All static resources have appropriate caching headers.

A+

Critical Rendering Path

No render-blocking resources

PASS

No render-blocking resources

No render-blocking resources detected

A+

Resource Hints

2 hints, 0 missing preconnects

PASS

2 hints, 0 missing preconnects

Page uses 2 resource hint(s)

Current Resource Hints

preconnect

—

preload

dns-prefetch

—

prefetch

—

2 resource hints configured

A+

Render-Blocking Resources

No render-blocking resources detected

PASS

No render-blocking resources detected

No render-blocking resources detected in <head>

A+

Third-Party Resources

No third-party resources detected

PASS

No third-party resources detected

Network Waterfall

115 requests over 5935ms

INFO

HTML JavaScript CSS Images Fonts XHR/Fetch Other

Third-Party Script Cost

Per-script blocking time, transfer cost, and cache headers

INFO

100% of JavaScript execution is third-party

First-party Third-party 7337ms · 1835KB · €80/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
Unattributable Unattributable	Other	1219ms	0 KB	—	€13/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	764ms	181 KB	32%	€8/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	570ms	164 KB	39%	€6/mo	Costly
www.rijksmuseum.nl www.rijksmuseum.nl	Other	476ms	109 KB	—	€5/mo	Costly
cdn-4.convertexperiments.com cdn-4.convertexperiments.com	Other	440ms	86 KB	52%	€5/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	369ms	137 KB	44%	€4/mo	Costly
www.rijksmuseum.nl www.rijksmuseum.nl	Other	364ms	10 KB	—	€4/mo	Costly
Microsoft Clarity scripts.clarity.ms	Session Replay	346ms	25 KB	—	€4/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	323ms	145 KB	42%	€4/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	302ms	136 KB	43%	€3/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	273ms	129 KB	48%	€3/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	261ms	134 KB	44%	€3/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	239ms	134 KB	44%	€3/mo	Costly
analytics.tiktok.com analytics.tiktok.com	Other	233ms	110 KB	57%	€3/mo	Costly
Hotjar script.hotjar.com	Session Replay	227ms	57 KB	67%	€2/mo	Costly
sc-static.net sc-static.net	Other	208ms	25 KB	—	€2/mo	Costly
www.rijksmuseum.nl www.rijksmuseum.nl	Other	205ms	52 KB	—	€2/mo	Costly
Facebook Pixel connect.facebook.net	Advertising	197ms	97 KB	33%	€2/mo	Optional
Facebook Pixel connect.facebook.net	Advertising	183ms	47 KB	—	€2/mo	Optional
LinkedIn Insight snap.licdn.com	Advertising	72ms	19 KB	—	€1/mo	Optional
analytics.tiktok.com analytics.tiktok.com	Other	67ms	40 KB	—	€1/mo	Optional

Unattributable

Other

Costly

Execution 1219ms

Transfer 0 KB

Monthly Cost €13/mo

Google Tag Manager

Tag Manager

Costly

Execution 764ms

Transfer 181 KB

Unused 32%

Monthly Cost €8/mo

Google Tag Manager

Tag Manager

Costly

Execution 570ms

Transfer 164 KB

Unused 39%

Monthly Cost €6/mo

www.rijksmuseum.nl

Other

Costly

Execution 476ms

Transfer 109 KB

Monthly Cost €5/mo

cdn-4.convertexperiments.com

Other

Costly

Execution 440ms

Transfer 86 KB

Unused 52%

Monthly Cost €5/mo

Google Tag Manager

Tag Manager

Costly

Execution 369ms

Transfer 137 KB

Unused 44%

Monthly Cost €4/mo

www.rijksmuseum.nl

Other

Costly

Execution 364ms

Transfer 10 KB

Monthly Cost €4/mo

Microsoft Clarity

Session Replay

Costly

Execution 346ms

Transfer 25 KB

Monthly Cost €4/mo

Google Tag Manager

Tag Manager

Costly

Execution 323ms

Transfer 145 KB

Unused 42%

Monthly Cost €4/mo

Google Tag Manager

Tag Manager

Costly

Execution 302ms

Transfer 136 KB

Unused 43%

Monthly Cost €3/mo

Google Tag Manager

Tag Manager

Costly

Execution 273ms

Transfer 129 KB

Unused 48%

Monthly Cost €3/mo

Google Tag Manager

Tag Manager

Costly

Execution 261ms

Transfer 134 KB

Unused 44%

Monthly Cost €3/mo

Google Tag Manager

Tag Manager

Costly

Execution 239ms

Transfer 134 KB

Unused 44%

Monthly Cost €3/mo

analytics.tiktok.com

Other

Costly

Execution 233ms

Transfer 110 KB

Unused 57%

Monthly Cost €3/mo

Hotjar

Session Replay

Costly

Execution 227ms

Transfer 57 KB

Unused 67%

Monthly Cost €2/mo

sc-static.net

Other

Costly

Execution 208ms

Transfer 25 KB

Monthly Cost €2/mo

www.rijksmuseum.nl

Other

Costly

Execution 205ms

Transfer 52 KB

Monthly Cost €2/mo

Facebook Pixel

Advertising

Optional

Execution 197ms

Transfer 97 KB

Unused 33%

Monthly Cost €2/mo

Facebook Pixel

Advertising

Optional

Execution 183ms

Transfer 47 KB

Monthly Cost €2/mo

LinkedIn Insight

Advertising

Optional

Execution 72ms

Transfer 19 KB

Monthly Cost €1/mo

analytics.tiktok.com

Other

Optional

Execution 67ms

Transfer 40 KB

Monthly Cost €1/mo

These scripts may cost more than they're worth

Unattributable adds 1219ms and costs ~€13/month
Google Tag Manager adds 764ms and costs ~€8/month
Google Tag Manager adds 570ms and costs ~€6/month
www.rijksmuseum.nl adds 476ms and costs ~€5/month
cdn-4.convertexperiments.com adds 440ms and costs ~€5/month
Google Tag Manager adds 369ms and costs ~€4/month
www.rijksmuseum.nl adds 364ms and costs ~€4/month
Microsoft Clarity adds 346ms and costs ~€4/month
Google Tag Manager adds 323ms and costs ~€4/month
Google Tag Manager adds 302ms and costs ~€3/month
Google Tag Manager adds 273ms and costs ~€3/month
Google Tag Manager adds 261ms and costs ~€3/month
Google Tag Manager adds 239ms and costs ~€3/month
analytics.tiktok.com adds 233ms and costs ~€3/month
Hotjar adds 227ms and costs ~€2/month
sc-static.net adds 208ms and costs ~€2/month
www.rijksmuseum.nl adds 205ms and costs ~€2/month

100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.

Why this matters

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 1219ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 764ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 570ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

www.rijksmuseum.nl takes 476ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

cdn-4.convertexperiments.com takes 440ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

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.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

Google Tag Manager takes 369ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

www.rijksmuseum.nl takes 364ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Microsoft Clarity takes 346ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 323ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 302ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 273ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 261ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 239ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

analytics.tiktok.com takes 233ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

57% of analytics.tiktok.com's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

Hotjar takes 227ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

67% of Hotjar's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

sc-static.net takes 208ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

www.rijksmuseum.nl takes 205ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

How third-party costs are calculated

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.