Skip to content
https://www.trainline.com

Performance

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

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

Mobile Desktop
66
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
94
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
92
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.

627 ms

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

1.08 s

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

595 ms

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

0.042

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

3.34 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.

4.64 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
14
5 PASS 2 REVIEW 5 FIX
F
Page Weight Budget
Action
2.7 MB transferred, 95 requests
FIX
2.7 MB transferred, 95 requests
Warning::
Page weighs 9.5 MB (2.7 MB transferred)
Warning::
JavaScript is 2.1 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 2.1 MB
Info::
95 HTTP requests
Info::
Estimated 0.56 g CO2 per page load
2.7 MB / 2.4 MB budget
2.7 MB transferred
95 requests
0.56 g CO2 per page load
JavaScript 2.1 MiB 80%
Other 189.3 KiB 7%
HTML 122.9 KiB 4%
CSS 66.8 KiB 2%
Images 44.3 KiB 2%
Other 42.3 KiB 2%
Fonts 41.6 KiB 2%
Other 26.1 KiB 1%
Other 0 B 0%
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 (2.7 MiB of 2.7 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Execution Cost
Action
2950ms total JS execution
FIX
2950ms total JS execution
Warning::
https://www.thetrainline.com/public/hweb/js/Home.1...: 922ms CPU time
Warning::
https://www.thetrainline.com/en-us: 477ms CPU time
Warning::
Unattributable: 341ms CPU time
Info::
https://www.thetrainline.com/public/hweb/js/vendor...: 225ms CPU time
Info::
https://www.thetrainline.com/public/hweb/js/app.89...: 200ms CPU time
Warning::
Third-party scripts: 2950ms (100% of total)

Main Thread Breakdown

Script Evaluation 56% Other 17% Script Parsing & Compilation 9% Style & Layout 8% Rendering 5% Garbage Collection 3%
ScriptTotalScriptingParse/CompileParty
https://www.thetrainline.com/public/hweb/js/Home.15c2810c2fc56a12ed5a.mjs922ms570ms67ms3rd
https://www.thetrainline.com/en-us477ms97ms18ms3rd
Unattributable341ms20ms0ms3rd
https://www.thetrainline.com/public/hweb/js/vendors.9ac2e1b9cc95010cc332.mjs225ms130ms74ms3rd
https://www.thetrainline.com/public/hweb/js/app.89b9a0d98d3ad67146be.mjs200ms195ms5ms3rd
https://cdn.cookielaw.org/scripttemplates/202601.2.0/otTCF.js178ms160ms3ms3rd
https://cdn.cookielaw.org/scripttemplates/202601.2.0/otBannerSdk.js142ms93ms18ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-NJRBF7N132ms92ms30ms3rd
https://dd.thetrainline.com/tags.js117ms101ms4ms3rd
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604020101/pubads_impl.js85ms58ms20ms3rd

Showing top 10 of 12 scripts

F
JS Bundles
Action
30 scripts, 1.0 MB unused
FIX
30 scripts, 1.0 MB unused
Warning::
https://www.thetrainline.com/public/hweb/js/Home.1...: 346 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...: 138 KB unused (75%)
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://accounts.google.com/gsi/client: 70 KB unused (76%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 1.0 MB
1051 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.thetrainline.com/public/hweb/js/Home.15c2810c2fc56a12ed5a.mjs611 KB346 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/m202604020101/pubads_impl.js183 KB138 KB (75%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-NJRBF7N193 KB76 KB (39%)✓3rd
https://accounts.google.com/gsi/client93 KB70 KB (76%)✓3rd
https://cdn.cookielaw.org/scripttemplates/202601.2.0/otBannerSdk.js128 KB61 KB (48%)✓3rd
https://www.thetrainline.com/public/hweb/js/google-one-tap.f6f095296acd8a81230d.mjs30 KB25 KB (84%)✓3rd
https://www.thetrainline.com/public/hweb/js/shareable-login-it-IT-json-translations.d58965399cff02397f7e.mjs4 KB—✓3rd
https://widget.trustpilot.com/trustboxes/54ad5defc6454f065c28af8b/main.js0 KB—✓3rd
https://widget.trustpilot.com/trustboxes/54ad5defc6454f065c28af8b/main.js18 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.

B
Image Optimization
15 images, 0 KB saveable
REVIEW
15 images, 0 KB saveable
Warning::
https://static.trainlinecontent.com/content/vul/lo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
15 images 44 KB
0 oversized -0 KB
15 legacy format
1 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

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 500 ms 1.0 s FCP 627 ms LCP 1.1 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
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
Network Waterfall
95 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 2950ms · 2052KB · $51/mo
www.thetrainline.com
Other
Costly
Execution 922ms
Transfer 611 KB
Unused 57%
Monthly Cost $16/mo
www.thetrainline.com
Other
Costly
Execution 477ms
Transfer 117 KB
Monthly Cost $8/mo
Unattributable
Other
Costly
Execution 341ms
Transfer 0 KB
Monthly Cost $6/mo
www.thetrainline.com
Other
Costly
Execution 225ms
Transfer 647 KB
Unused 52%
Monthly Cost $4/mo
www.thetrainline.com
Other
Optional
Execution 200ms
Transfer 48 KB
Monthly Cost $3/mo
OneTrust
Consent
Essential
Execution 178ms
Transfer 18 KB
Monthly Cost $3/mo
OneTrust
Consent
Essential
Execution 142ms
Transfer 128 KB
Unused 48%
Monthly Cost $2/mo
Google Tag Manager
Tag Manager
Optional
Execution 132ms
Transfer 193 KB
Unused 39%
Monthly Cost $2/mo
dd.thetrainline.com
Other
Optional
Execution 117ms
Transfer 43 KB
Monthly Cost $2/mo
securepubads.g.doubleclick.net
Other
Optional
Execution 85ms
Transfer 183 KB
Unused 75%
Monthly Cost $1/mo
js-agent.newrelic.com
Other
Optional
Execution 67ms
Transfer 30 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

  • www.thetrainline.com adds 922ms and costs ~$16/month
  • www.thetrainline.com adds 477ms and costs ~$8/month
  • Unattributable adds 341ms and costs ~$6/month
  • www.thetrainline.com adds 225ms 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 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

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 477ms 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 341ms 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 225ms 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

75% 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.

Send Feedback