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Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
84
GRADE
B
FIX
3
REVIEW
2
PASS
9
INFO
2

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

Mobile Desktop
40
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.

3.91 s

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

11.47 s

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

836 ms

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

0.090

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

5.94 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.

11.47 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
16
9 PASS 2 REVIEW 3 FIX
D
JS Execution Cost
Action
3345ms total JS execution
FIX
3345ms total JS execution
Warning::
Unattributable: 841ms CPU time
Warning::
https://www.sncf-connect.com/widget/web-widgets-v1...: 728ms CPU time
Warning::
https://dd.sncf-connect.com/tags.js: 363ms CPU time
Warning::
https://securepubads.g.doubleclick.net/pagead/mana...: 305ms CPU time
Info::
https://didomi.sncf-connect.com/sdk/c8e2e67c354c0d...: 194ms CPU time
Warning::
Third-party scripts: 1995ms (60% of total)

Main Thread Breakdown

Script Evaluation 55% Other 17% Script Parsing & Compilation 10% Style & Layout 9% Garbage Collection 6%
ScriptTotalScriptingParse/CompileParty
Unattributable841ms158ms0ms3rd
https://www.sncf-connect.com/widget/web-widgets-v1.0.0.js728ms531ms140ms1st
https://dd.sncf-connect.com/tags.js363ms323ms10ms3rd
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604020101/pubads_impl.js305ms236ms50ms3rd
https://didomi.sncf-connect.com/sdk/c8e2e67c354c0d6dec2981e079061b37f6a1f337/modern/sdk.c8e2e67c354c0d6dec2981e079061b37f6a1f337.js194ms164ms29ms3rd
https://www.sncf-connect.com/assets/js/js_GPvrhW60mafr0YU742BMfwPu569xjJXhcNVbwO6YHTM.js?scope=footer&delta=3&language=fr-FR&theme=mercure_sb&include=eJxtkFGOwzAIRC9Ub45kEZs6bglUgFP19kuk_YhX_bHlNzMYADP03PmBxUWXh_3IK9_RvB9AltHxtqOWoZhtXaBOL3LUNCwOhn0yFuADLJkDV9A6S1rTS6WO4lfeSFagiHyoc7sqG6qkiEl8RVeBgNuAhsne3UvYJhFblGPxXqbWdrQtgQamiVtRIZpr2B7GtALzP85QnsFnOFo7Fyd8NjvNPLgfqHaOh6Blu2rvXhv6GfEvmKR1vh1W8iryjMUsf3esEO-d6BeuJa6v161ms16ms1ms1st
https://didomi.sncf-connect.com/sdk/c8e2e67c354c0d6dec2981e079061b37f6a1f337/modern/ui-web-fr-web.c8e2e67c354c0d6dec2981e079061b37f6a1f337.js156ms77ms20ms3rd
https://www.sncf-connect.com/151ms39ms7ms1st
https://www.sncf-connect.com/sdk/sdk-v1.10.0.js126ms104ms16ms1st
https://www.sncf-connect.com/widget/024759151b7cf920e852.web-widgets-v1.0.0-chunk.js97ms53ms28ms1st

Showing top 10 of 13 scripts

D
JS Bundles
Action
23 scripts, 364 KB unused
FIX
23 scripts, 364 KB unused
Warning::
https://www.sncf-connect.com/widget/web-widgets-v1...: 154 KB unused (51%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://securepubads.g.doubleclick.net/pagead/mana...: 130 KB unused (71%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.datadoghq-browser-agent.com/eu1/v6/dat...: 46 KB unused (80%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://didomi.sncf-connect.com/sdk/c8e2e67c354c0d...: 34 KB unused (38%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 364 KB
364 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.sncf-connect.com/widget/web-widgets-v1.0.0.js304 KB154 KB (51%)✓1st
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604020101/pubads_impl.js183 KB130 KB (71%)✓3rd
https://www.datadoghq-browser-agent.com/eu1/v6/datadog-rum.js58 KB46 KB (80%)✓3rd
https://didomi.sncf-connect.com/sdk/c8e2e67c354c0d6dec2981e079061b37f6a1f337/modern/sdk.c8e2e67c354c0d6dec2981e079061b37f6a1f337.js90 KB34 KB (38%)✓3rd
https://www.sncf-connect.com/themes/custom/mercure_sb/dist/js/00-base/global/widget-cart-init.js?tcih7w0 KB—✓1st
https://www.sncf-connect.com/themes/custom/mercure_sb/dist/vendors/js/ad-common.js?tcih7w3 KB—✓1st
https://www.sncf-connect.com/themes/custom/mercure_sb/dist/js/00-base/global/widget-login-init.js?tcih7w1 KB—✓1st
https://www.sncf-connect.com/assets/js/js_GPvrhW60mafr0YU742BMfwPu569xjJXhcNVbwO6YHTM.js?scope=footer&delta=3&language=fr-FR&theme=mercure_sb&include=eJxtkFGOwzAIRC9Ub45kEZs6bglUgFP19kuk_YhX_bHlNzMYADP03PmBxUWXh_3IK9_RvB9AltHxtqOWoZhtXaBOL3LUNCwOhn0yFuADLJkDV9A6S1rTS6WO4lfeSFagiHyoc7sqG6qkiEl8RVeBgNuAhsne3UvYJhFblGPxXqbWdrQtgQamiVtRIZpr2B7GtALzP85QnsFnOFo7Fyd8NjvNPLgfqHaOh6Blu2rvXhv6GfEvmKR1vh1W8iryjMUsf3esEO-d6BeuJa6v6 KB—✓1st
https://www.sncf-connect.com/assets/asset_injector/js/op_festivals_ete-5d4e072bc1616bb010d062287615a45b.js?tcih7w0 KB—✓1st
https://www.sncf-connect.com/assets/js/js_u1AZ9v72ME4UB-mH-zEleVwcdODBjfaT3bLBMsuHs60.js?scope=footer&delta=5&language=fr-FR&theme=mercure_sb&include=eJxtkFGOwzAIRC9Ub45kEZs6bglUgFP19kuk_YhX_bHlNzMYADP03PmBxUWXh_3IK9_RvB9AltHxtqOWoZhtXaBOL3LUNCwOhn0yFuADLJkDV9A6S1rTS6WO4lfeSFagiHyoc7sqG6qkiEl8RVeBgNuAhsne3UvYJhFblGPxXqbWdrQtgQamiVtRIZpr2B7GtALzP85QnsFnOFo7Fyd8NjvNPLgfqHaOh6Blu2rvXhv6GfEvmKR1vh1W8iryjMUsf3esEO-d6BeuJa6v2 KB—✓1st

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

D
HTTP Caching
Action
no-store (uncacheable)
FIX
no-store (uncacheable)
Info::
Cache-Control: no-store prevents all caching
Intentional for dynamic content, but increases server load for every page view.
Got: max-age=0, private, no-cache, no-store, must-revalidate
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

max-age=0, private, no-cache, no-store, must-revalidate

DirectiveValueMeaning
max-age0Cache for 0 seconds
private—Only browser cache, not CDN/proxy
no-cache—Cache but always revalidate first
no-store—Never cache this response
must-revalidate—Must recheck with server after expiry
C
Page Weight Budget
Action
1.6 MB transferred, 56 requests
REVIEW
1.6 MB transferred, 56 requests
Info::
Page weighs 4.7 MB (1.6 MB transferred)
Warning::
JavaScript is 968 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 968 KB
Info::
56 HTTP requests
Info::
Estimated 0.34 g CO2 per page load
1.6 MB / 2.4 MB budget
1.6 MB transferred
56 requests
0.34 g CO2 per page load
JavaScript 967.9 KiB 58%
Images 480.2 KiB 29%
Fonts 80.6 KiB 5%
CSS 76.7 KiB 5%
HTML 42.6 KiB 3%
Other 29.1 KiB 2%
Other 3.2 KiB 0%
Other 3.0 KiB 0%
0 2.4 MB 4.9 MB
Approaching limit

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

B
Image Optimization
9 images, 0 KB saveable
REVIEW
9 images, 0 KB saveable
Warning::
https://www.sncf-connect.com/didomi-popin-handshak... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sncf-connect.com/# is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
9 images 480 KB
0 oversized -0 KB
2 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

A
Third-Party Impact
33% third-party, 0 ms blocking
PASS
33% third-party, 0 ms blocking
Info::
Third-party code accounts for 33% of page weight (549.3 KiB of 1.6 MiB)
Info::
Third-party blocking time is low (0 ms)
67%
33%
First-party Third-party
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+
Font Loading
3 fonts (81 KB)
PASS
3 fonts (81 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

81 KB total

Render-blocking

0

of 3

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s FCP 3.9 s LCP 11.5 shttps://www.sncf-connect.com/themes/custom/mercure_sb/dist/fonts/AvenirMedium.woff2AvenirMedium.woff2 https://www.sncf-connect.com/themes/custom/mercure_sb/dist/fonts/AvenirMedium.woff2 — 11.0 KiB — 0 ms — font-display: swaphttps://www.sncf-connect.com/themes/custom/mercure_sb/dist/fonts/AvenirHeavy.woff2AvenirHeavy.woff2 https://www.sncf-connect.com/themes/custom/mercure_sb/dist/fonts/AvenirHeavy.woff2 — 41.4 KiB — 0 ms — font-display: swaphttps://www.sncf-connect.com/themes/custom/mercure_sb/dist/fonts/AvenirNextRoundedProBold.woff2AvenirNextRoundedProBol... https://www.sncf-connect.com/themes/custom/mercure_sb/dist/fonts/AvenirNextRoundedProBold.woff2 — 28.2 KiB — 0 ms — font-display: swap
AvenirMedium.woff2 woff2 swap
Size 11 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
AvenirHeavy.woff2 woff2 swap
Size 41 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
AvenirNextRoundedProBol... woff2 swap
Size 28 KB
Load time 0 ms
Start 0 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
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
A+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
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

Network Waterfall
56 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
60% of JavaScript execution is third-party
First-party Third-party 1995ms · 421KB · $26/mo
Unattributable
Other
Costly
Execution 841ms
Transfer 0 KB
Monthly Cost $11/mo
dd.sncf-connect.com
Other
Costly
Execution 363ms
Transfer 43 KB
Monthly Cost $5/mo
securepubads.g.doubleclick.net
Other
Costly
Execution 305ms
Transfer 183 KB
Unused 71%
Monthly Cost $4/mo
didomi.sncf-connect.com
Other
Optional
Execution 194ms
Transfer 90 KB
Unused 38%
Monthly Cost $3/mo
didomi.sncf-connect.com
Other
Optional
Execution 156ms
Transfer 54 KB
Monthly Cost $2/mo
tags.tiqcdn.com
Other
Optional
Execution 72ms
Transfer 18 KB
Monthly Cost $1/mo
securepubads.g.doubleclick.net
Other
Optional
Execution 65ms
Transfer 34 KB
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • Unattributable adds 841ms and costs ~$11/month
  • dd.sncf-connect.com adds 363ms and costs ~$5/month
  • securepubads.g.doubleclick.net adds 305ms and costs ~$4/month

60% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

Learn more ▾

Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

Unattributable takes 841ms 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

dd.sncf-connect.com takes 363ms 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

securepubads.g.doubleclick.net takes 305ms 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

71% of securepubads.g.doubleclick.net'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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