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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
83
GRADE
B
FIX
1
REVIEW
5
PASS
6
INFO
2

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

Mobile Desktop
93
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
100
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
100
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

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

915 ms

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

1.58 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.

1.10 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.

1.58 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
6 PASS 5 REVIEW 1 FIX
D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (1.6 MiB of 1.6 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
C
Page Weight Budget
Action
1.6 MB transferred, 76 requests
REVIEW
1.6 MB transferred, 76 requests
Info::
Page weighs 3.9 MB (1.6 MB transferred)
Info::
CSS is 685 KB — consider purging unused styles
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
Got: 685 KB
Warning::
JavaScript is 530 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 530 KB
Info::
76 HTTP requests
Info::
Estimated 0.34 g CO2 per page load
1.6 MB / 2.4 MB budget
1.6 MB transferred
76 requests
0.34 g CO2 per page load
CSS 685.2 KiB 42%
JavaScript 530.2 KiB 32%
Images 392.0 KiB 24%
HTML 22.1 KiB 1%
Other 6.1 KiB 0%
Other 917 B 0%
Other 0 B 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Approaching limit

Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.

Why this matters

CSS bundle is large — purge unused styles (PurgeCSS, Tailwind JIT) to reduce CSS payload.

Source: web.dev

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Why this matters

JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.

Source: web.dev

C
Image Optimization
Action
12 images, 0 KB saveable
REVIEW
12 images, 0 KB saveable
Warning::
https://webtools.europa.eu/images/flags/eu.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://european-union.europa.eu/themes/contrib/oe... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
12 images 386 KB
0 oversized -0 KB
9 legacy format
2 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

C
JS Bundles
Action
28 scripts, 248 KB unused
REVIEW
28 scripts, 248 KB unused
Warning::
https://european-union.europa.eu/sites/default/fil...: 66 KB unused (90%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://european-union.europa.eu/sites/default/fil...: 60 KB unused (82%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://webtools.europa.eu/js/webtools.etrans.js?t...: 36 KB unused (31%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://webtools.europa.eu/load.js: 22 KB unused (55%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://webtools.europa.eu/load.js: 22 KB unused (55%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 248 KB
248 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://european-union.europa.eu/sites/default/files/js/js_JP6x4lPIakp0N_pEt4lfZguYmvs1ixMQFHYBOHl9z9E.js?scope=footer&delta=3&language=en&theme=ewcms_theme&include=eJxVy9EOgjAMheEXQnmkpoyTOdOtpO1A3l5BjfGu5_tTbKk61S5RpLTcWUacdHcSPiCDGrJG4SjahneNGypGJPJuK_Z_PW9uLHuU5IPiE5LWRRtakJTJ2HZC_1U8AvZ6Il_zoRumUBUfZ-sLy_W7L17ZQpRn2BOXg0xX74 KB66 KB (90%)✓3rd
https://european-union.europa.eu/sites/default/files/js/js_JP6x4lPIakp0N_pEt4lfZguYmvs1ixMQFHYBOHl9z9E.js?scope=footer&delta=3&language=en&theme=ewcms_theme&include=eJyVjdEOgzAIRX_IrZ9EsBIloWAo1bmvnzNdlj3uDc49F2jPpcJizk_TQIFC2hLm4I0gHFkGupTSJFhY54aSOsK8sF6aVsFg079kUAM5__RSLFQoUYbafKPjl14zKsoRnOtg1INsZTUljfPS6OgHUPum9AjyswR1m990pzHMpKbJ24py_-y3WtBDDCfyF6mcboQ74 KB60 KB (82%)✓3rd
https://webtools.europa.eu/js/webtools.etrans.js?t=dc2f2ded115 KB36 KB (31%)✓3rd
https://webtools.europa.eu/load.js0 KB22 KB (55%)✓3rd
https://webtools.europa.eu/load.js42 KB22 KB (55%)✓3rd
https://european-union.europa.eu/core/assets/vendor/jquery/jquery.min.js?v=4.0.0-rc.10 KB21 KB (77%)✓3rd
https://european-union.europa.eu/core/assets/vendor/jquery/jquery.min.js?v=4.0.0-rc.127 KB21 KB (77%)✓3rd
https://webtools.europa.eu/js/webtools.sbkm.2.0.js?t=dc2f2ded19 KB—✓3rd
https://webtools.europa.eu/js/webtools.globan.js?t=dc2f2ded35 KB—✓3rd
https://ec.europa.eu/wel/surveys/wr_survey03/data/survey_url_rules.js?986440v0.630 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

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

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

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

B
HTTP Caching
no-cache
REVIEW
no-cache
Info::
Cache-Control header is set
Got: no-cache
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

no-cache

DirectiveValueMeaning
no-cache—Cache but always revalidate first
A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
JS Execution Cost
277ms total JS execution
PASS
277ms total JS execution
Info::
https://webtools.europa.eu/load.js: 120ms CPU time
Info::
https://european-union.europa.eu/index_en: 81ms CPU time
Info::
Unattributable: 76ms CPU time
Warning::
Third-party scripts: 277ms (100% of total)

Main Thread Breakdown

Other 30% Script Evaluation 29% Style & Layout 21% Script Parsing & Compilation 10% Parse HTML & CSS 7% Rendering 3%
ScriptTotalScriptingParse/CompileParty
https://webtools.europa.eu/load.js120ms59ms10ms3rd
https://european-union.europa.eu/index_en81ms1ms0ms3rd
Unattributable76ms2ms0ms3rd
A+
Font Loading
No web fonts (system fonts)
PASS
No web fonts (system fonts)
Info::
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
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
Network Waterfall
76 requests over 0ms
INFO

Performance analysis not available for this result.

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 277ms · 18KB · €3/mo
webtools.europa.eu
Other
Optional
Execution 120ms
Transfer 0 KB
Unused 55%
Monthly Cost €1/mo
european-union.europa.eu
Other
Optional
Execution 81ms
Transfer 18 KB
Monthly Cost €1/mo
Unattributable
Other
Optional
Execution 76ms
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

55% of webtools.europa.eu'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.

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