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
6 images, 0 KB saveable
REVIEW
6 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.
6images8 KB
0oversized-0 KB
6legacy format
3missing dimensionsCLS 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::
i
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
TransferFOIT (block)FOUT (swap)
TLCircular-Bold.woff2woff2swap
Size40 KB
Load time68 ms
Start1.2 s
RiskFOUT — text flashes from fallback to web font
font-woff;charset=utf-8...woffswap
Size2 KB
Load time116 ms
Start1.7 s
RiskFOUT — 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
62 requests over 2747ms
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-party6848ms · 1949KB · $118/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
www.thetrainline.com
www.thetrainline.com
Other
2327ms
606 KB
58%
$40/mo
Costly
www.thetrainline.com
www.thetrainline.com
Other
1466ms
120 KB
—
$25/mo
Costly
www.thetrainline.com
www.thetrainline.com
Other
619ms
647 KB
52%
$11/mo
Costly
www.thetrainline.com
www.thetrainline.com
Other
587ms
48 KB
—
$10/mo
Costly
Unattributable
Unattributable
Other
536ms
0 KB
—
$9/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
314ms
194 KB
39%
$5/mo
Costly
dd.thetrainline.com
dd.thetrainline.com
Other
223ms
39 KB
—
$4/mo
Costly
securepubads.g.doubleclick.net
securepubads.g.doubleclick.net
Other
182ms
187 KB
77%
$3/mo
Optional
js-agent.newrelic.com
js-agent.newrelic.com
Other
172ms
30 KB
—
$3/mo
Optional
www.thetrainline.com
www.thetrainline.com
Other
164ms
2 KB
—
$3/mo
Optional
cdn.branch.io
cdn.branch.io
Other
117ms
23 KB
—
$2/mo
Optional
securepubads.g.doubleclick.net
securepubads.g.doubleclick.net
Other
79ms
34 KB
—
$1/mo
Optional
www.thetrainline.com
www.thetrainline.com
Other
61ms
18 KB
—
$1/mo
Optional
www.thetrainline.com
Other
Costly
Execution2327ms
Transfer606 KB
Unused58%
Monthly Cost$40/mo
www.thetrainline.com
Other
Costly
Execution1466ms
Transfer120 KB
Monthly Cost$25/mo
www.thetrainline.com
Other
Costly
Execution619ms
Transfer647 KB
Unused52%
Monthly Cost$11/mo
www.thetrainline.com
Other
Costly
Execution587ms
Transfer48 KB
Monthly Cost$10/mo
Unattributable
Other
Costly
Execution536ms
Transfer0 KB
Monthly Cost$9/mo
Google Tag Manager
Tag Manager
Costly
Execution314ms
Transfer194 KB
Unused39%
Monthly Cost$5/mo
dd.thetrainline.com
Other
Costly
Execution223ms
Transfer39 KB
Monthly Cost$4/mo
securepubads.g.doubleclick.net
Other
Optional
Execution182ms
Transfer187 KB
Unused77%
Monthly Cost$3/mo
js-agent.newrelic.com
Other
Optional
Execution172ms
Transfer30 KB
Monthly Cost$3/mo
www.thetrainline.com
Other
Optional
Execution164ms
Transfer2 KB
Monthly Cost$3/mo
cdn.branch.io
Other
Optional
Execution117ms
Transfer23 KB
Monthly Cost$2/mo
securepubads.g.doubleclick.net
Other
Optional
Execution79ms
Transfer34 KB
Monthly Cost$1/mo
www.thetrainline.com
Other
Optional
Execution61ms
Transfer18 KB
Monthly Cost$1/mo
These scripts may cost more than they're worth
www.thetrainline.com adds 2327ms and costs ~$40/month
www.thetrainline.com adds 1466ms and costs ~$25/month
www.thetrainline.com adds 619ms and costs ~$11/month
www.thetrainline.com adds 587ms and costs ~$10/month
Unattributable adds 536ms and costs ~$9/month
Google Tag Manager adds 314ms and costs ~$5/month
dd.thetrainline.com adds 223ms 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 2327ms 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
58% 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 1466ms 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 619ms 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 587ms 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 536ms 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 314ms 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 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
77% 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.