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https://uni-koeln.de

Performance

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

SCORE

92

GRADE

A

FIX

0

REVIEW

3

PASS

10

INFO

2

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

100

Performance

96

Accessibility

96

Best Practices

92

SEO

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

374 ms

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

434 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.

0.001

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

820 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.

436 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

15

10 PASS 3 REVIEW

C

Image Optimization

Action

10 images, 0 KB saveable

REVIEW

10 images, 0 KB saveable

https://uni-koeln.de/sites/uni/_processed_/9/6/csm... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://uni-koeln.de/sites/uni/_processed_/1/5/csm... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://uni-koeln.de/fileadmin/_processed_/a/f/csm... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://uni-koeln.de/sites/uni/_processed_/f/1/csm... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

10 images 710 KB

0 oversized -0 KB

9 legacy format

4 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

B

JS Execution Cost

549ms total JS execution

REVIEW

549ms total JS execution

https://uni-koeln.de/: 451ms CPU time

Unattributable: 97ms CPU time

Third-party scripts: 97ms (18% of total)

Main Thread Breakdown

Other 40% Style & Layout 34% Rendering 15% Script Evaluation 7% Parse HTML & CSS 4%

Script	Total	Scripting	Parse/Compile	Party
https://uni-koeln.de/	451ms	3ms	1ms	1st
Unattributable	97ms	6ms	0ms	3rd

C

Green Hosting

Action

Whether the site is served from green-energy infrastructure

REVIEW

Green Hosting

No green hosting detected

A

Page Weight Budget

946 KB transferred, 25 requests

PASS

946 KB transferred, 25 requests

Page weighs 1.8 MB (946 KB transferred)

25 HTTP requests

Estimated 0.19 g CO2 per page load

946 KB transferred

25 requests

0.19 g CO2 per page load

Images 709.9 KiB 75%

HTML 60.8 KiB 6%

Other 56.0 KiB 6%

JavaScript 52.9 KiB 6%

CSS 35.1 KiB 4%

Fonts 31.7 KiB 3%

Other 192 B 0%

0 2.4 MB 4.9 MB

Under budget

A+

Third-Party Impact

2% third-party, 0 ms blocking

PASS

2% third-party, 0 ms blocking

Third-party code accounts for 2% of page weight (22.1 KiB of 946.5 KiB)

Third-party blocking time is low (0 ms)

98%

First-party Third-party

A+

Text Compression

All text resources are compressed

PASS

All text resources are compressed

All text resources are compressed

All text resources are properly compressed.

A+

Font Loading

1 fonts (32 KB)

PASS

1 fonts (32 KB)

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

Web fonts

1

32 KB total

Render-blocking

0

of 1

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

albert-sans-latin-wght-... woff2 swap

Size 32 KB

Load time 169 ms

Start 1.0 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+

JS Bundles

5 scripts, 0 KB unused

PASS

5 scripts, 0 KB unused

0 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://uni-koeln.de/typo3conf/ext/uzk2025/Resources/Public/Js/main-8eAe4pPs.js	5 KB	—	✓	1st
https://uni-koeln.de/typo3conf/ext/powermail/Resources/Public/JavaScript/Powermail/Form.min.js?1753202143	23 KB	—	✓	1st
https://matomo.rrz.uni-koeln.de/matomo.js	22 KB	—	✓	3rd
https://uni-koeln.de/typo3conf/ext/uzk2025/Resources/Public/Js/animated-news-teaser-BHP9S2X_.js	1 KB	—	✓	1st
https://uni-koeln.de/typo3conf/ext/uzk2025/Resources/Public/Js/forms-Du4ZAIZx.js	1 KB	—	✓	1st

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+

Page Weight Inventory

25 resources · 946 KB · 0 KB savings available

PASS

25 resources · 946 KB · 0 KB savings available

Within 1MB page-weight target

Got: 946 KB

3 third-party resources (2% of weight)

1 resources over 200KB

25 resources · 946.5 KiB · 3 third-party Within 1MB page-weight target

Image 81% · 765.9 KiB

Document 6% · 61.0 KiB

JavaScript 6% · 52.9 KiB

CSS 4% · 35.1 KiB

Font 3% · 31.7 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

25 resources			946.5 KiB

A

HTTP Caching

max-age=85676 (23 hours)

PASS

max-age=85676 (23 hours)

Cache-Control header is set

Got: max-age=85676

Effective TTL: 23 hours (max-age=85676)

No ETag or Last-Modified header

Conditional requests (304 Not Modified) are not possible without validators.

Cache-Control

max-age=85676

Directive	Value	Meaning
max-age	85676	Cache for 23 hours

Effective TTL: 85676 seconds

Network Waterfall

25 requests over 2722ms

INFO

HTML JavaScript CSS Images Fonts XHR/Fetch Other

Third-Party Script Cost

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

INFO

18% of JavaScript execution is third-party

First-party Third-party 97ms · 0KB · €1/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
Unattributable Unattributable	Other	97ms	0 KB	—	€1/mo	Optional

Unattributable

Other

Optional

Execution 97ms

Transfer 0 KB

Monthly Cost €1/mo

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.

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