Performance

· 26 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

Accessibility

100

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.

2.86 s

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

3.47 s

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

328 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.

3.07 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.

5.31 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 s

Checks

14 PASS 7 REVIEW 2 FIX

JS Execution Cost

Action

4267ms total JS execution

FIX

4267ms total JS execution

https://svennouwen.nl/: 2131ms CPU time

https://svennouwen.nl/wp-includes/js/jquery/jquery...: 995ms CPU time

Unattributable: 504ms CPU time

https://svennouwen.nl/wp-content/plugins/jupiterx-...: 289ms CPU time

https://svennouwen.nl/wp-content/themes/jupiterx/l...: 127ms CPU time

Main Thread Breakdown

Script Evaluation 29% Other 28% Style & Layout 26% Script Parsing & Compilation 7% Parse HTML & CSS 6% Rendering 5%

Script	Total	Scripting	Parse/Compile	Party
https://svennouwen.nl/	2131ms	46ms	28ms	1st
https://svennouwen.nl/wp-includes/js/jquery/jquery.min.js?ver=3.7.1	995ms	826ms	19ms	1st
Unattributable	504ms	13ms	0ms	1st
https://svennouwen.nl/wp-content/plugins/jupiterx-core/includes/extensions/raven/assets/js/frontend.min.js?ver=7.1.2	289ms	143ms	145ms	1st
https://svennouwen.nl/wp-content/themes/jupiterx/lib/assets/dist/js/frontend.min.js?ver=4.61.0	127ms	49ms	30ms	1st
https://svennouwen.nl/wp-content/plugins/jupiterx-core/includes/extensions/raven/assets/css/frontend.min.css?ver=7.1.2	109ms	0ms	0ms	1st
https://svennouwen.nl/wp-includes/js/wp-emoji-release.min.js?ver=7.1.2	56ms	48ms	6ms	1st
https://svennouwen.nl/wp-content/plugins/elementor/assets/js/frontend.min.js?ver=4.3.2	55ms	34ms	13ms	1st

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

4 images, 0 KB saveable

REVIEW

4 images, 0 KB saveable

All images are well-optimized

4 images 142 KB

0 oversized -0 KB

4 legacy format

0 missing dimensions CLS risk

JS Bundles

Action

17 scripts, 196 KB unused

REVIEW

17 scripts, 196 KB unused

https://svennouwen.nl/wp-content/plugins/jupiterx-...: 163 KB unused (86%)

Consider code splitting or tree shaking to reduce unused code.

https://svennouwen.nl/wp-content/themes/jupiterx/l...: 32 KB unused (84%)

Consider code splitting or tree shaking to reduce unused code.

Total unused JavaScript: 196 KB

196 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://svennouwen.nl/wp-content/plugins/jupiterx-core/includes/extensions/raven/assets/js/frontend.min.js?ver=7.1.2	191 KB	163 KB (86%)	✓	1st
https://svennouwen.nl/wp-content/themes/jupiterx/lib/assets/dist/js/frontend.min.js?ver=4.61.0	39 KB	32 KB (84%)	✓	1st
https://svennouwen.nl/wp-content/plugins/elementor/assets/js/frontend.min.js?ver=4.3.2	19 KB	—	✓	1st
https://svennouwen.nl/wp-includes/js/wp-util.min.js?ver=7.1.2	1 KB	—	✓	1st
https://svennouwen.nl/wp-content/themes/jupiterx/lib/assets/dist/js/utils.min.js?ver=4.61.0	0 KB	—	✓	1st
https://svennouwen.nl/wp-content/plugins/elementor/assets/js/webpack.runtime.min.js?ver=4.3.2	0 KB	—	✓	1st
https://svennouwen.nl/wp-content/plugins/elementor/assets/js/frontend-modules.min.js?ver=4.3.2	16 KB	—	✓	1st
https://svennouwen.nl/wp-includes/js/jquery/ui/core.min.js?ver=1.14.2	7 KB	—	✓	1st
https://svennouwen.nl/wp-includes/js/jquery/jquery.min.js?ver=3.7.1	30 KB	—	✓	1st
https://svennouwen.nl/wp-includes/js/underscore.min.js?ver=1.13.8	7 KB	—	✓	1st

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

HTTP/3 (QUIC)

HTTP/3 not advertised

REVIEW

HTTP/3 not advertised

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.

Document Compression

Document response uses gzip; brotli would be ~20% smaller

REVIEW

Document response uses gzip; brotli would be ~20% smaller

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.

Main HTML Cache-Control

No Cache-Control header on main HTML response

REVIEW

No Cache-Control header on main HTML response

Main HTML response has no Cache-Control header

Without an explicit Cache-Control, browsers fall back to heuristic caching (~10% of Last-Modified age). Set `Cache-Control: no-cache` or `max-age=300` for HTML to control freshness explicitly -- prevents stale auth state and SPA shell drift.

Server-Timing Observability

No Server-Timing header found

REVIEW

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.

JavaScript Blocking

2 JS blocking issue(s) detected

REVIEW

2 JS blocking issue(s) detected

12 render-blocking <script src> tag(s) without async/defer

Each `<script src=...>` without `async`, `defer`, or `type="module"` blocks HTML parsing while the browser fetches and executes it. The block lasts the entire round-trip + execution time -- on slow networks this translates directly into LCP delay. Add `defer` (executes after parse, in source order) for scripts that interact with the DOM, or `async` (executes whenever ready) for analytics / independent scripts. Module scripts (`type="module"`) are deferred by default.

Total JS execution time is 4.3 s -- over the 3.5s budget

Total JavaScript execution (parse + compile + run) across all scripts exceeds 3.5 seconds. On low-end devices that becomes 7-15+ seconds and shows up directly in TBT and INP. Reduce by: tree-shaking unused dependencies, code-splitting (dynamic `import()`), removing or deferring third-party tracking, and replacing heavy frameworks where they're not needed.

Page Weight Budget

728 KB transferred, 50 requests

PASS

728 KB transferred, 50 requests

Page weighs 2.7 MB (728 KB transferred)

50 HTTP requests

Estimated 0.15 g CO2 per page load

728 KB transferred

50 requests

0.15 g CO2 per page load

JavaScript 358.8 KiB 49%

CSS 156.7 KiB 22%

Images 142.0 KiB 20%

Fonts 50.2 KiB 7%

HTML 18.8 KiB 3%

Other 1.2 KiB 0%

Other 170 B 0%

0 2.4 MB 4.9 MB

Under budget

A+

Third-Party Impact

7% third-party, 0 ms blocking

PASS

7% third-party, 0 ms blocking

Third-party code accounts for 7% of page weight (51.8 KiB of 727.8 KiB)

Third-party blocking time is low (0 ms)

93%

First-party Third-party

A+

Text Compression

All text resources are compressed

PASS

All text resources are compressed

All text resources are properly compressed.

A+

Font Loading

4 fonts (50 KB)

PASS

4 fonts (50 KB)

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

Web fonts

50 KB total

Render-blocking

of 4

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

plus-jakarta-sans-latin... woff2 swap

Size 12 KB

Load time 9 ms

Start 1.2 s

Risk FOUT — text flashes from fallback to web font

plus-jakarta-sans-latin... woff2 swap

Size 13 KB

Load time 19 ms

Start 1.2 s

Risk FOUT — text flashes from fallback to web font

plus-jakarta-sans-latin... woff2 swap

Size 13 KB

Load time 26 ms

Start 1.2 s

Risk FOUT — text flashes from fallback to web font

plus-jakarta-sans-latin... woff2 swap

Size 13 KB

Load time 13 ms

Start 1.3 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

1 hints, 0 missing preconnects

PASS

1 hints, 0 missing preconnects

Page uses 1 resource hint(s)

Current Resource Hints

preconnect

preload

—

dns-prefetch

—

prefetch

—

1 resource hints configured

A+

LCP Image Preload

LCP preload audit not available

PASS

LCP preload audit not available

LCP image preload audit not available for this scan

A+

Server Response Intelligence

2 server-response signal(s) detected

PASS

2 server-response signal(s) detected

`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).

No `ETag` or `Last-Modified` -- conditional GET not supported

Without either header, browsers can't issue conditional GETs and refresh always re-downloads the full response body even when nothing changed. Add `ETag: "<hash>"` (or `Last-Modified: <date>`) on cacheable responses; the server returns 304 Not Modified when the client's cached copy is still valid, saving bandwidth.

A+

Page Weight Inventory

50 resources · 728 KB · 196 KB savings available

PASS

50 resources · 728 KB · 196 KB savings available

Within 1MB page-weight target

Got: 728 KB

~196 KB of savings available

6 third-party resources (7% of weight)

50 resources · 727.8 KiB · 6 third-party Within 1MB page-weight target

JavaScript 49% · 358.8 KiB

CSS 22% · 156.7 KiB

Image 20% · 143.2 KiB

Font 7% · 50.2 KiB

Document 3% · 18.8 KiB

Other 0% · 170 B

~195.6 KiB of savings available

Remove unused JavaScript: 195.6 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

50 resources			727.8 KiB

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

CSS Performance Depth

1 CSS depth issue(s) detected

PASS

1 CSS depth issue(s) detected

22 render-blocking stylesheet(s) -- recommended: <=3

Each `<link rel="stylesheet">` without a non-blocking `media` attribute holds up the first paint. Browsers download all of them before painting any content. Consolidate into 1-2 critical-path stylesheets; defer non-critical CSS via `<link rel="stylesheet" media="print" onload="this.media='all'">` or via the loadCSS pattern; inline above-the-fold CSS in `<style>` to short-circuit the request entirely.

A+

Green Hosting

Whether the site is served from green-energy infrastructure

PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Combell

Asset Compression

No text asset hosts to measure

INFO

No text asset hosts to measure

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

50 requests over 1928ms

INFO

HTML JavaScript CSS Images Fonts XHR/Fetch Other

Image Optimization

5 images, 54 KB total, 36 KB wasted

INFO

Image Optimization Audit

Total Images

Total Size

54 KB

Oversized

Wasted

36 KB

3 missing lazy loading

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