Performance

· 22 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

SEO

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

1.01 s

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

1.33 s

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.

0.021

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

1.01 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.

1.33 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

13 PASS 4 REVIEW 2 FIX

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 (913.8 KiB of 914.1 KiB)

Third-party blocking time is low (0 ms)

100%

First-party Third-party

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.

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.

Compression Algorithm

Action

Main response served uncompressed

REVIEW

Main response served uncompressed

Main HTML response has no Content-Encoding (uncompressed)

The main HTML document is served without compression. The Text Compression section above lists the broader picture; for the main response specifically, even gzip would shave ~70-80% off most text payloads.

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.

Page Weight Budget

914 KB transferred, 28 requests

PASS

914 KB transferred, 28 requests

Page weighs 1.9 MB (914 KB transferred)

28 HTTP requests

Estimated 0.19 g CO2 per page load

914 KB transferred

28 requests

0.19 g CO2 per page load

Images 553.8 KiB 61%

JavaScript 173.9 KiB 19%

Fonts 131.1 KiB 14%

HTML 46.9 KiB 5%

CSS 5.1 KiB 1%

Other 1.4 KiB 0%

Other 1.2 KiB 0%

Other 833 B 0%

0 2.4 MB 4.9 MB

Under budget

A+

Text Compression

All text resources are compressed

PASS

All text resources are compressed

All text resources are properly compressed.

A+

Image Optimization

11 images, 0 KB saveable

PASS

11 images, 0 KB saveable

All images are well-optimized

11 images 554 KB

0 oversized -0 KB

1 legacy format

0 missing dimensions CLS risk

A+

JS Execution Cost

440ms total JS execution

PASS

440ms total JS execution

https://www.bzh-freiburg.de/en: 194ms CPU time

https://consent.cookiebot.com/uc.js: 141ms CPU time

Unattributable: 105ms CPU time

Third-party scripts: 440ms (100% of total)

Main Thread Breakdown

Other 36% Script Evaluation 23% Style & Layout 18% Rendering 12% Parse HTML & CSS 5% Script Parsing & Compilation 4%

Script	Total	Scripting	Parse/Compile	Party
https://www.bzh-freiburg.de/en	194ms	2ms	0ms	3rd
https://consent.cookiebot.com/uc.js	141ms	101ms	4ms	3rd
Unattributable	105ms	1ms	0ms	3rd

A+

Font Loading

3 fonts (131 KB)

PASS

3 fonts (131 KB)

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

Web fonts

131 KB total

Render-blocking

of 3

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

dbcfebeb-81b6-4dd3-912a... woff2 swap

Size 51 KB

Load time 82 ms

Start 380 ms

Risk FOUT — text flashes from fallback to web font

3a9dc726-d61e-48d0-86ba... woff2 swap

Size 32 KB

Load time 55 ms

Start 381 ms

Risk FOUT — text flashes from fallback to web font

3ca076a2-34ad-4c48-a029... woff2 swap

Size 48 KB

Load time 80 ms

Start 383 ms

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+

JS Bundles

5 scripts, 50 KB unused

PASS

5 scripts, 50 KB unused

https://consent.cookiebot.com/26772e78-659e-4424-a...: 26 KB unused (25%)

Consider code splitting or tree shaking to reduce unused code.

https://www.bzh-freiburg.de/vendor/swiper/swiper-b...: 24 KB unused (59%)

Consider code splitting or tree shaking to reduce unused code.

Total unused JavaScript: 50 KB

50 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://consent.cookiebot.com/26772e78-659e-4424-a95b-9b89f6bceb65/cc.js?renew=false&referer=www.bzh-freiburg.de&dnt=false&init=false&culture=en	104 KB	26 KB (25%)	✓	3rd
https://www.bzh-freiburg.de/vendor/swiper/swiper-bundle.min.js	41 KB	24 KB (59%)	✓	3rd
https://consent.cookiebot.com/uc.js	27 KB	—	✓	3rd
https://consentcdn.cookiebot.com/consentconfig/26772e78-659e-4424-a95b-9b89f6bceb65/bzh-freiburg.de/configuration.js	1 KB	—	✓	3rd
https://www.bzh-freiburg.de/scripts/bzh_custom_footer-script.js	1 KB	—	✓	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

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

No optimization needed

PASS

No optimization needed

No resource hint issues

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.

Page Weight Inventory

28 resources · 914 KB · 50 KB savings available

PASS

28 resources · 914 KB · 50 KB savings available

Within 1MB page-weight target

Got: 914 KB

27 third-party resources (100% of weight)

28 resources · 914.1 KiB · 27 third-party Within 1MB page-weight target

Image 61% · 554.8 KiB

JavaScript 19% · 173.9 KiB

Font 14% · 131.1 KiB

Document 5% · 47.3 KiB

CSS 1% · 5.1 KiB

Other 0% · 2.0 KiB

~49.5 KiB of savings available

Remove unused JavaScript: 49.5 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

28 resources			914.1 KiB

A+

Green Hosting

Whether the site is served from green-energy infrastructure

PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Hetzner Online GmbH

Network Waterfall

28 requests over 789ms

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 440ms · 73KB · €5/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
www.bzh-freiburg.de www.bzh-freiburg.de	Other	194ms	46 KB	—	€2/mo	Optional
consent.cookiebot.com consent.cookiebot.com	Other	141ms	27 KB	—	€2/mo	Optional
Unattributable Unattributable	Other	105ms	0 KB	—	€1/mo	Optional

www.bzh-freiburg.de

Other

Optional

Execution 194ms

Transfer 46 KB

Monthly Cost €2/mo

consent.cookiebot.com

Other

Optional

Execution 141ms

Transfer 27 KB

Monthly Cost €2/mo

Unattributable

Other

Optional

Execution 105ms

Transfer 0 KB

Monthly Cost €1/mo

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

How third-party costs are calculated

Image Optimization

14 images, 508 KB total, 0 KB wasted

INFO

Image Optimization Audit

Total Images

Total Size

508 KB

Oversized

7 missing alt text 6 missing dimensions 6 missing lazy loading

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