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https://stackexchange.com

Performance

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

SCORE

87

GRADE

B

FIX

1

REVIEW

3

PASS

9

INFO

2

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

99

Performance

80

Accessibility

81

Best Practices

91

SEO

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

660 ms

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

937 ms

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

4 ms

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.

826 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.

1.15 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

15

9 PASS 3 REVIEW 1 FIX

D

Third-Party Impact

Action

89% third-party, 0 ms blocking

FIX

89% third-party, 0 ms blocking

Third-party code accounts for 89% of page weight (303.3 KiB of 339.8 KiB)

Third-party blocking time is low (0 ms)

89%

First-party Third-party

C

Image Optimization

Action

69 images, 0 KB saveable

REVIEW

69 images, 0 KB saveable

https://stackexchange.com/Content/Img/hero/close.p... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://stackexchange.com/Content/Img/hero/vote.pn... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://stackexchange.com/Content/Img/hero/bubble.... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://stackexchange.com/Content/Img/hero/check.p... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

69 images 141 KB

0 oversized -0 KB

69 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 Bundles

5 scripts, 0 KB unused

REVIEW

5 scripts, 0 KB unused

https://cdn.sstatic.net/stackexchange/Js/master.js...: unminified — 5 KB could be saved

https://cdn.sstatic.net/stackexchange/Js/topbar.js...: unminified — 5 KB could be saved

0 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js	30 KB	—	✓	3rd
https://cdn.sstatic.net/stackexchange/Js/master.js?v=ef8b6ed08310	10 KB	—	✗	3rd
https://cdn.sstatic.net/stackexchange/Js/universal-login.js?v=30968200101f	2 KB	—	✓	3rd
https://cdn.sstatic.net/stackexchange/Js/topbar.js?v=b2367277c351	11 KB	—	✗	3rd
https://stackexchange.com/cdn-cgi/challenge-platform/h/b/scripts/jsd/0b8fb825cb67/main.js?	11 KB	—	✓	1st

B

HTTP Caching

private

REVIEW

private

Cache-Control header is set

Got: private

No ETag or Last-Modified header

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

Cache-Control

private

Directive	Value	Meaning
private	—	Only browser cache, not CDN/proxy

A+

Page Weight Budget

340 KB transferred, 80 requests

PASS

340 KB transferred, 80 requests

Page weighs 1.0 MB (340 KB transferred)

80 HTTP requests

Estimated 0.07 g CO2 per page load

340 KB transferred

80 requests

0.07 g CO2 per page load

Images 141.4 KiB 42%

CSS 113.8 KiB 33%

JavaScript 65.6 KiB 19%

HTML 15.9 KiB 5%

Other 2.0 KiB 1%

Other 1021 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 compressed

All text resources are properly compressed.

A+

JS Execution Cost

500ms total JS execution

PASS

500ms total JS execution

https://stackexchange.com/: 215ms CPU time

Unattributable: 167ms CPU time

https://stackexchange.com/cdn-cgi/challenge-platfo...: 117ms CPU time

Third-party scripts: 167ms (33% of total)

Main Thread Breakdown

Other 36% Script Evaluation 30% Style & Layout 15% Rendering 9% Parse HTML & CSS 6%

Script	Total	Scripting	Parse/Compile	Party
https://stackexchange.com/	215ms	25ms	2ms	1st
Unattributable	167ms	4ms	0ms	3rd
https://stackexchange.com/cdn-cgi/challenge-platform/scripts/jsd/main.js	117ms	109ms	5ms	1st

A+

Font Loading

No web fonts (system fonts)

PASS

No web fonts (system fonts)

No web fonts loaded — system fonts are fastest

No web fonts loaded — system fonts are optimal.

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

80 resources · 340 KB · 0 KB savings available

PASS

80 resources · 340 KB · 0 KB savings available

Within 1MB page-weight target

Got: 340 KB

72 third-party resources (89% of weight)

80 resources · 339.8 KiB · 72 third-party Within 1MB page-weight target

Image 42% · 143.0 KiB

CSS 33% · 113.8 KiB

JavaScript 19% · 65.6 KiB

Document 5% · 15.9 KiB

Other 0% · 1.4 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

80 resources			339.8 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: Cloudflare

Network Waterfall

80 requests over 1052ms

INFO

HTML JavaScript CSS Images Fonts XHR/Fetch Other

Third-Party Script Cost

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

INFO

33% of JavaScript execution is third-party

First-party Third-party 167ms · 0KB · $2/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
Unattributable Unattributable	Other	167ms	0 KB	—	$2/mo	Optional

Unattributable

Other

Optional

Execution 167ms

Transfer 0 KB

Monthly Cost $2/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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