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https://www.leon.co.uk

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
90
GRADE
A
FIX
2
REVIEW
3
PASS
7
INFO
2

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

Mobile Desktop
82
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
57
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
85
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
91
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.

3.05 s

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

3.05 s

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

290 ms

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

0.000

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

3.05 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.

4.59 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
7 PASS 3 REVIEW 2 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 (192.1 KiB of 192.1 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
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
JS Execution Cost
750ms total JS execution
REVIEW
750ms total JS execution
Warning::
https://www.googletagmanager.com/gtag/js?id=G-F7VW...: 313ms CPU time
Info::
Unattributable: 245ms CPU time
Info::
https://www.google-analytics.com/analytics.js: 112ms CPU time
Info::
https://leon.co.uk/: 79ms CPU time
Warning::
Third-party scripts: 750ms (100% of total)

Main Thread Breakdown

Script Evaluation 59% Other 24% Script Parsing & Compilation 11% Style & Layout 5%
ScriptTotalScriptingParse/CompileParty
https://www.googletagmanager.com/gtag/js?id=G-F7VWD6N0RY&cx=c&_slc=1313ms236ms70ms3rd
Unattributable245ms103ms0ms3rd
https://www.google-analytics.com/analytics.js112ms93ms9ms3rd
https://leon.co.uk/79ms12ms2ms3rd
B
JS Bundles
2 scripts, 63 KB unused
REVIEW
2 scripts, 63 KB unused
Warning::
https://www.googletagmanager.com/gtag/js?id=G-F7VW...: 63 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 63 KB
63 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtag/js?id=G-F7VWD6N0RY&cx=c&_slc=1146 KB63 KB (43%)✓3rd
https://www.google-analytics.com/analytics.js21 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

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

Green Hosting

No green hosting detected

A+
Page Weight Budget
192 KB transferred, 10 requests
PASS
192 KB transferred, 10 requests
Info::
Page weighs 489 KB (192 KB transferred)
Info::
10 HTTP requests
Info::
Estimated 0.04 g CO2 per page load
192 KB / 2.4 MB budget
192 KB transferred
10 requests
0.04 g CO2 per page load
JavaScript 167.3 KiB 87%
Fonts 12.2 KiB 6%
Images 7.3 KiB 4%
Other 2.4 KiB 1%
HTML 971 B 0%
CSS 954 B 0%
Other 544 B 0%
Other 461 B 0%
0 2.4 MB 4.9 MB
Under budget
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
Image Optimization
1 images, 0 KB saveable
PASS
1 images, 0 KB saveable
Warning::
https://leon.co.uk/info-at-leon.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
1 images 7 KB
0 oversized -0 KB
1 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

A+
Font Loading
1 fonts (12 KB)
PASS
1 fonts (12 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

12 KB total

Render-blocking

0

of 1

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 1.0 s 2.0 s 3.0 s FCP 3.1 s LCP 3.1 shttps://fonts.gstatic.com/s/josefinsans/v34/Qw3PZQNVED7rKGKxtqIqX5E-AVSJrOCfjY46_DjQbMZhLybvUVw.woff2Qw3PZQNVED7rKGKxtqIqX5E... https://fonts.gstatic.com/s/josefinsans/v34/Qw3PZQNVED7rKGKxtqIqX5E-AVSJrOCfjY46_DjQbMZhLybvUVw.woff2 — 12.2 KiB — 0 ms — font-display: swap
Qw3PZQNVED7rKGKxtqIqX5E... woff2 swap
Size 12 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
Network Waterfall
10 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 750ms · 168KB · £8/mo
Google Tag Manager
Tag Manager
Costly
Execution 313ms
Transfer 146 KB
Unused 43%
Monthly Cost £3/mo
Unattributable
Other
Costly
Execution 245ms
Transfer 0 KB
Monthly Cost £3/mo
Google Analytics
Analytics
Optional
Execution 112ms
Transfer 21 KB
Monthly Cost £1/mo
leon.co.uk
Other
Optional
Execution 79ms
Transfer 1 KB
Monthly Cost £1/mo

These scripts may cost more than they're worth

  • Google Tag Manager adds 313ms and costs ~£3/month
  • Unattributable adds 245ms and costs ~£3/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

Google Tag Manager takes 313ms 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 245ms 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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