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https://www.trainline.com

Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
74
GRADE
C
FIX
5
REVIEW
2
PASS
7
INFO
2

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

Mobile Desktop
32
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
96
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
96
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
92
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.

2.89 s

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

18.04 s

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

3.86 s

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.

8.95 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.

19.96 s

Page Load Progression

851 ms
1.7 s
2.6 s
3.4 s
4.3 s
5.1 s
6.0 s
6.8 s
Checks
16
7 PASS 2 REVIEW 5 FIX
D
Page Weight Budget
Action
2.5 MB transferred, 78 requests
FIX
2.5 MB transferred, 78 requests
Warning::
Page weighs 9.1 MB (2.5 MB transferred)
Warning::
JavaScript is 2.0 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 2.0 MB
Info::
78 HTTP requests
Info::
Estimated 0.53 g CO2 per page load
2.5 MB / 2.4 MB budget
2.5 MB transferred
78 requests
0.53 g CO2 per page load
JavaScript 2.0 MiB 80%
Other 187.3 KiB 7%
HTML 125.4 KiB 5%
CSS 60.8 KiB 2%
Other 42.5 KiB 2%
Fonts 41.6 KiB 2%
Other 26.1 KiB 1%
Images 25.4 KiB 1%
0 2.4 MB 4.9 MB
Over budget

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

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 (2.5 MiB of 2.5 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
JS Execution Cost
Action
10997ms total JS execution
FIX
10997ms total JS execution
Warning::
https://www.thetrainline.com/public/hweb/js/Home.1...: 3585ms CPU time
Warning::
https://www.thetrainline.com/en-us: 1669ms CPU time
Warning::
Unattributable: 922ms CPU time
Warning::
https://www.thetrainline.com/public/hweb/js/vendor...: 877ms CPU time
Warning::
https://www.thetrainline.com/public/hweb/js/app.89...: 810ms CPU time
Warning::
Third-party scripts: 10997ms (100% of total)

Main Thread Breakdown

Script Evaluation 58% Other 16% Script Parsing & Compilation 9% Style & Layout 8% Rendering 5%
ScriptTotalScriptingParse/CompileParty
https://www.thetrainline.com/public/hweb/js/Home.15c2810c2fc56a12ed5a.mjs3585ms2191ms257ms3rd
https://www.thetrainline.com/en-us1669ms315ms72ms3rd
Unattributable922ms90ms0ms3rd
https://www.thetrainline.com/public/hweb/js/vendors.9ac2e1b9cc95010cc332.mjs877ms500ms311ms3rd
https://www.thetrainline.com/public/hweb/js/app.89b9a0d98d3ad67146be.mjs810ms791ms18ms3rd
https://cdn.cookielaw.org/scripttemplates/202601.2.0/otTCF.js714ms664ms9ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-NJRBF7N484ms358ms95ms3rd
https://cdn.cookielaw.org/scripttemplates/202601.2.0/otBannerSdk.js483ms301ms67ms3rd
https://dd.thetrainline.com/tags.js370ms314ms18ms3rd
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604060101/pubads_impl.js?cb=31097718249ms169ms76ms3rd

Showing top 10 of 15 scripts

F
JS Bundles
Action
27 scripts, 962 KB unused
FIX
27 scripts, 962 KB unused
Warning::
https://www.thetrainline.com/public/hweb/js/Home.1...: 350 KB unused (57%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.thetrainline.com/public/hweb/js/vendor...: 335 KB unused (52%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://securepubads.g.doubleclick.net/pagead/mana...: 139 KB unused (76%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-NJR...: 76 KB unused (39%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cdn.cookielaw.org/scripttemplates/202601.2...: 61 KB unused (48%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 962 KB
962 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.thetrainline.com/public/hweb/js/Home.15c2810c2fc56a12ed5a.mjs611 KB350 KB (57%)✓3rd
https://www.thetrainline.com/public/hweb/js/vendors.9ac2e1b9cc95010cc332.mjs647 KB335 KB (52%)✓3rd
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604060101/pubads_impl.js?cb=31097718183 KB139 KB (76%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-NJRBF7N193 KB76 KB (39%)✓3rd
https://cdn.cookielaw.org/scripttemplates/202601.2.0/otBannerSdk.js128 KB61 KB (48%)✓3rd
https://www.thetrainline.com/public/hweb/js/shareable-login-it-IT-json-translations.d58965399cff02397f7e.mjs4 KB—✓3rd
https://www.thetrainline.com/public/hweb/js/80862.ab86151296010e8724fa.mjs8 KB—✓3rd
blob:https://www.thetrainline.com/d1595545-b86c-40c3-acac-1fc6b0cff410-0 KB—✓3rd
https://cdn.cookielaw.org/scripttemplates/otSDKStub.js9 KB—✓3rd
https://www.thetrainline.com/public/hweb/js/shareable-header-register-overlay.b9bf76aa76ba7718356b.mjs6 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

F
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
No Cache-Control header found
Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

C
Image Optimization
Action
8 images, 0 KB saveable
REVIEW
8 images, 0 KB saveable
Warning::
https://static.trainlinecontent.com/content/WEB/im... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://static.trainlinecontent.com/content/WEB/im... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://static.trainlinecontent.com/content/WEB/im... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
8 images 25 KB
0 oversized -0 KB
8 legacy format
3 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

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

Green Hosting

No green hosting detected

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
2 fonts (42 KB)
PASS
2 fonts (42 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

42 KB total

Render-blocking

0

of 2

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 14.0 s 16.0 s 18.0 s FCP 2.9 s LCP 18.0 shttps://www.thetrainline.com/content/WEB/fonts/tl-circular-1.0.1/TLCircular-Bold.woff2TLCircular-Bold.woff2 https://www.thetrainline.com/content/WEB/fonts/tl-circular-1.0.1/TLCircular-Bold.woff2 — 40.0 KiB — 0 ms — font-display: swapdata:application/font-woff;charset=utf-8;base64, d09GRgABAAAAAAZgABAAAAAADAAAAAAAAAAAAAAAAAAAAAAAAA…font-woff;charset=utf-8... data:application/font-woff;charset=utf-8;base64, d09GRgABAAAAAAZgABAAAAAADAAAAAAAAAAAAAAAAAAAAAAAAA… — 1.6 KiB — 0 ms — font-display: swap
TLCircular-Bold.woff2 woff2 swap
Size 40 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
font-woff;charset=utf-8... woff swap
Size 2 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
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
7 hints, 0 missing preconnects
PASS
7 hints, 0 missing preconnects
Info::
Page uses 7 resource hint(s)

Current Resource Hints

preconnect
—
preload
7
dns-prefetch
—
prefetch
—

7 resource hints configured

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
Network Waterfall
78 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 10997ms · 2089KB · $190/mo
www.thetrainline.com
Other
Costly
Execution 3585ms
Transfer 611 KB
Unused 57%
Monthly Cost $62/mo
www.thetrainline.com
Other
Costly
Execution 1669ms
Transfer 120 KB
Monthly Cost $29/mo
Unattributable
Other
Costly
Execution 922ms
Transfer 0 KB
Monthly Cost $16/mo
www.thetrainline.com
Other
Costly
Execution 877ms
Transfer 647 KB
Unused 52%
Monthly Cost $15/mo
www.thetrainline.com
Other
Costly
Execution 810ms
Transfer 48 KB
Monthly Cost $14/mo
OneTrust
Consent
Essential
Execution 714ms
Transfer 18 KB
Monthly Cost $12/mo
Google Tag Manager
Tag Manager
Costly
Execution 484ms
Transfer 193 KB
Unused 39%
Monthly Cost $8/mo
OneTrust
Consent
Essential
Execution 483ms
Transfer 128 KB
Unused 48%
Monthly Cost $8/mo
dd.thetrainline.com
Other
Costly
Execution 370ms
Transfer 43 KB
Monthly Cost $6/mo
securepubads.g.doubleclick.net
Other
Costly
Execution 249ms
Transfer 183 KB
Unused 76%
Monthly Cost $4/mo
js-agent.newrelic.com
Other
Costly
Execution 241ms
Transfer 30 KB
Monthly Cost $4/mo
www.thetrainline.com
Other
Costly
Execution 219ms
Transfer 2 KB
Monthly Cost $4/mo
securepubads.g.doubleclick.net
Other
Optional
Execution 159ms
Transfer 34 KB
Monthly Cost $3/mo
OneTrust
Consent
Essential
Execution 149ms
Transfer 9 KB
Monthly Cost $3/mo
cdn.branch.io
Other
Optional
Execution 65ms
Transfer 23 KB
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • www.thetrainline.com adds 3585ms and costs ~$62/month
  • www.thetrainline.com adds 1669ms and costs ~$29/month
  • Unattributable adds 922ms and costs ~$16/month
  • www.thetrainline.com adds 877ms and costs ~$15/month
  • www.thetrainline.com adds 810ms and costs ~$14/month
  • Google Tag Manager adds 484ms and costs ~$8/month
  • dd.thetrainline.com adds 370ms and costs ~$6/month
  • securepubads.g.doubleclick.net adds 249ms and costs ~$4/month
  • js-agent.newrelic.com adds 241ms and costs ~$4/month
  • www.thetrainline.com adds 219ms and costs ~$4/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.thetrainline.com takes 3585ms 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

57% of www.thetrainline.com'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

www.thetrainline.com takes 1669ms 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

Unattributable takes 922ms 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.thetrainline.com takes 877ms 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

52% of www.thetrainline.com'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

www.thetrainline.com takes 810ms 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

Google Tag Manager takes 484ms 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.thetrainline.com takes 370ms 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 249ms 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

76% 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

js-agent.newrelic.com takes 241ms 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.thetrainline.com takes 219ms 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

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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