Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
100
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
100
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.
First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.
393 ms
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
777 ms
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
0 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.049
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
590 ms
Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.
794 ms
Page Load Progression
375 ms
750 ms
1.1 s
1.5 s
1.9 s
2.2 s
2.6 s
3.0 s
Checks
23
14 PASS5 REVIEW
C
Image Optimization
Action
14 images, 0 KB saveable
REVIEW
14 images, 0 KB saveable
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/9/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/nissewaard/sit... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/f/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/9/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/9/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/4/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/0/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/a/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/2/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.nissewaard.nl/fileadmin/_processed_/8/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
14images552 KB
0oversized-0 KB
10legacy format
10missing dimensionsCLS 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
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
B
HTTP/3 (QUIC)
HTTP/3 not advertised
REVIEW
HTTP/3 not advertised
Info::
i
HTTP/3 (QUIC) is not advertised
HTTP/3 isn't advertised via Alt-Svc and the worker didn't negotiate h3. HTTP/3 reduces handshake latency (1-RTT instead of 2-3 RTTs) and is more resilient on lossy connections. Most modern CDNs (Cloudflare, Fastly, AWS CloudFront, Google Cloud CDN) support HTTP/3 with a single config switch -- consider enabling for mobile-heavy workloads.
B
Document Compression
Document response uses gzip; brotli would be ~20% smaller
REVIEW
Document response uses gzip; brotli would be ~20% smaller
Info::
i
Main HTML response uses gzip (brotli would be ~20% smaller)
All current browsers support brotli. Most CDNs (Cloudflare, Fastly, AWS CloudFront, Vercel, Netlify) can switch from gzip to brotli with a single config flag. Origin servers (nginx, Apache) need a brotli module compiled in -- nginx-brotli or Apache mod_brotli.
B
Server-Timing Observability
No Server-Timing header found
REVIEW
No Server-Timing header found
Info::
i
No Server-Timing header found
Server-Timing exposes backend timing breakdowns to browser DevTools (e.g., `db: 45ms; render: 120ms; cache: 2ms`). Useful for diagnosing slow pages without backend log access. Most modern frameworks (Next.js, Cloudflare Workers, Fastly) emit it automatically; absence on a managed platform usually means telemetry headers are stripped at the edge.
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
A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
✓
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
✓
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
✓
No resource hint issues
A+
LCP Image Preload
LCP preload audit not available
PASS
LCP preload audit not available
Info::
✓
LCP image preload audit not available for this scan
A+
Main HTML Cache-Control
Main HTML uses no-cache -- safe revalidate-on-request policy
PASS
Main HTML uses no-cache -- safe revalidate-on-request policy
Info::
✓
Main HTML uses no-cache -- safe revalidate-on-request policy
Got: no-cache
A+
Server Response Intelligence
2 server-response signal(s) detected
PASS
2 server-response signal(s) detected
Info::
✓
`Vary` header declared: Accept-Encoding
The page declares a `Vary` header, telling downstream caches which request headers the response varies on. Critical for content-negotiated responses (compression, language, cookies, device class).
Whether the site is served from green-energy infrastructure
PASS
Green Hosting
This site is hosted on green energy infrastructure
Provider: Leaseweb Global BV
Asset Compression
No text asset hosts to measure
INFO
No text asset hosts to measure
Info::
i
No third-party or subdomain host served enough text assets to measure
Asset compression is measured per host, from one HEAD request against a sampled resource. Pages that serve all their JS and CSS from the document's own origin are covered by the document compression check instead.
Network Waterfall
80 requests over 666ms
INFO
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Real-User Performance (CrUX)
Field metrics from the Chrome User Experience Report
INFO
Chrome User Experience (CrUX)
Real-user metrics from the Chrome UX Report (2026-10-14 — 2026-11-10)
LCP (p75)
771 ms
98% good
INP (p75)
70 ms
99% good
CLS (p75)
0.000
92% good
FCP (p75)
735 ms
TTFB (p75)
368 ms
This origin passes Core Web Vitals assessment
Image Optimization
10 images, 365 KB total, 0 KB wasted
INFO
Image Optimization Audit
Total Images
10
Total Size
365 KB
10 missing dimensions9 missing lazy loading
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.
