Performance

· 17 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

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.

4.13 s

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

7.47 s

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

14 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.194

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

4.57 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.

8.54 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

10 PASS 4 REVIEW 1 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 (1.1 MiB of 1.1 MiB)

Third-party blocking time is low (0 ms)

100%

First-party Third-party

Page Weight Budget

1.1 MB transferred, 42 requests

REVIEW

1.1 MB transferred, 42 requests

Page weighs 2.1 MB (1.1 MB transferred)

42 HTTP requests

Estimated 0.23 g CO2 per page load

1.1 MB transferred

42 requests

0.23 g CO2 per page load

Images 725.7 KiB 64%

JavaScript 255.4 KiB 23%

Fonts 81.7 KiB 7%

CSS 41.9 KiB 4%

HTML 21.1 KiB 2%

Other 1.2 KiB 0%

Other 147 B 0%

Other 86 B 0%

0 2.4 MB 4.9 MB

Under budget

JS Execution Cost

914ms total JS execution

REVIEW

914ms total JS execution

https://www.ademe.fr/: 254ms CPU time

https://www.ademe.fr/wp-includes/js/jquery/jquery....: 223ms CPU time

Unattributable: 179ms CPU time

https://www.googletagmanager.com/gtm.js?id=GTM-5KQ...: 158ms CPU time

https://tarteaucitron.io/load.js?domain=www.ademe....: 100ms CPU time

Third-party scripts: 914ms (100% of total)

Main Thread Breakdown

Script Evaluation 38% Other 27% Style & Layout 17% Script Parsing & Compilation 8% Parse HTML & CSS 7% Rendering 4%

Script	Total	Scripting	Parse/Compile	Party
https://www.ademe.fr/	254ms	36ms	4ms	3rd
https://www.ademe.fr/wp-includes/js/jquery/jquery.min.js?ver=3.7.1	223ms	101ms	9ms	3rd
Unattributable	179ms	5ms	0ms	3rd
https://www.googletagmanager.com/gtm.js?id=GTM-5KQTZDQP	158ms	114ms	29ms	3rd
https://tarteaucitron.io/load.js?domain=www.ademe.fr&uuid=2df1000bf385655312abede8e30421664e7d594e	100ms	66ms	9ms	3rd

JS Bundles

15 scripts, 95 KB unused

REVIEW

15 scripts, 95 KB unused

https://www.googletagmanager.com/gtm.js?id=GTM-5KQ...: 68 KB unused (55%)

Consider code splitting or tree shaking to reduce unused code.

https://cdn.tarteaucitron.io/tarteaucitron.service...: 27 KB unused (75%)

Consider code splitting or tree shaking to reduce unused code.

Total unused JavaScript: 95 KB

95 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://www.googletagmanager.com/gtm.js?id=GTM-5KQTZDQP	124 KB	68 KB (55%)	✓	3rd
https://cdn.tarteaucitron.io/tarteaucitron.services.min.js?v=1.32.0	36 KB	27 KB (75%)	✓	3rd
https://cdntag.tarteaucitron.io/load.js?domain=www.ademe.fr&uuid=2df1000bf385655312abede8e30421664e7d594e	23 KB	—	✓	3rd
https://www.ademe.fr/wp-content/plugins/who-at-internet/js/who_ati.js	0 KB	—	✓	3rd
https://www.ademe.fr/wp-content/cache/min/1/wp-content/plugins/notibar/assets/frontend/js/notibar.js?ver=1776244742	3 KB	—	✓	3rd
https://www.ademe.fr/wp-content/themes/ademe/js/scripts.min.js?ver=e6728d	2 KB	—	✓	3rd
https://www.ademe.fr/wp-includes/js/jquery/jquery.min.js?ver=3.7.1	29 KB	—	✓	3rd
https://www.ademe.fr/wp-content/cache/min/1/wp-content/themes/ademe/dist/theme/front.js?ver=1776244742	2 KB	—	✓	3rd
https://www.ademe.fr/wp-content/plugins/wp-rocket/assets/js/lazyload/17.8.3/lazyload.min.js	3 KB	—	✓	3rd
https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da1771523124516	11 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

Page Weight Inventory

42 resources · 1.1 MB · 95 KB savings available

REVIEW

42 resources · 1.1 MB · 95 KB savings available

Page weight 103 KB over 1MB target

Got: 1.1 MB Expected: ≤ 1 MB

~95 KB of savings available

41 third-party resources (100% of weight)

1 resources over 200KB

42 resources · 1.1 MiB · 41 third-party 103.3 KiB over 1MB target

Image 64% · 726.3 KiB

JavaScript 23% · 255.4 KiB

Font 7% · 81.7 KiB

CSS 4% · 41.9 KiB

Document 2% · 21.8 KiB

Other 0% · 233 B

~94.6 KiB of savings available

Remove unused JavaScript: 94.6 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

42 resources			1.1 MiB

A+

Text Compression

All text resources are compressed

PASS

All text resources are compressed

All text resources are properly compressed.

Image Optimization

15 images, 0 KB saveable

PASS

15 images, 0 KB saveable

All images are well-optimized

15 images 726 KB

0 oversized -0 KB

3 legacy format

0 missing dimensions CLS risk

A+

Font Loading

2 fonts (82 KB)

PASS

2 fonts (82 KB)

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

Web fonts

82 KB total

Render-blocking

of 2

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

Marianne-Regular.woff2 woff2 swap

Size 40 KB

Load time 34 ms

Start 956 ms

Risk FOUT — text flashes from fallback to web font

Marianne-Bold.woff2 woff2 swap

Size 41 KB

Load time 32 ms

Start 957 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+

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+

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

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

HTTP Caching

max-age=3600 (1 hour)

PASS

max-age=3600 (1 hour)

Cache-Control header is set

Got: max-age=3600

Effective TTL: 1 hour (max-age=3600)

No ETag or Last-Modified header

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

Cache-Control

max-age=3600

Directive	Value	Meaning
max-age	3600	Cache for 1 hour

Effective TTL: 3600 seconds

Network Waterfall

42 requests over 2781ms

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 914ms · 174KB · €10/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
www.ademe.fr www.ademe.fr	Other	254ms	21 KB	—	€3/mo	Costly
www.ademe.fr www.ademe.fr	Other	223ms	29 KB	—	€2/mo	Costly
Unattributable Unattributable	Other	179ms	0 KB	—	€2/mo	Optional
Google Tag Manager www.googletagmanager.com	Tag Manager	158ms	124 KB	55%	€2/mo	Optional
tarteaucitron.io tarteaucitron.io	Other	100ms	0 KB	—	€1/mo	Optional

www.ademe.fr

Other

Costly

Execution 254ms

Transfer 21 KB

Monthly Cost €3/mo

www.ademe.fr

Other

Costly

Execution 223ms

Transfer 29 KB

Monthly Cost €2/mo

Unattributable

Other

Optional

Execution 179ms

Transfer 0 KB

Monthly Cost €2/mo

Google Tag Manager

Tag Manager

Optional

Execution 158ms

Transfer 124 KB

Unused 55%

Monthly Cost €2/mo

tarteaucitron.io

Other

Optional

Execution 100ms

Transfer 0 KB

Monthly Cost €1/mo

These scripts may cost more than they're worth

www.ademe.fr adds 254ms and costs ~€3/month
www.ademe.fr adds 223ms and costs ~€2/month

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

www.ademe.fr takes 254ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

www.ademe.fr takes 223ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

55% of Google Tag Manager's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

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.