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https://www.nhs.uk

Performance

· 13 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
93
GRADE
A
FIX
1
REVIEW
1
PASS
10
INFO
1

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

Mobile Desktop
86
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.

497 ms

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

937 ms

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

0 ms

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

0.241

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

1.41 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.

937 ms

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
13
10 PASS 1 REVIEW 1 FIX
D
Third-Party Impact
Action
87% third-party, 0 ms blocking
FIX
87% third-party, 0 ms blocking
Warning::
Third-party code accounts for 87% of page weight (538.7 KiB of 622.7 KiB)
Info::
Third-party blocking time is low (0 ms)
87%
First-party Third-party
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Page Weight Budget
623 KB transferred, 13 requests
PASS
623 KB transferred, 13 requests
Info::
Page weighs 1.0 MB (623 KB transferred)
Info::
13 HTTP requests
Info::
Estimated 0.13 g CO2 per page load
623 KB / 2.4 MB budget
623 KB transferred
13 requests
0.13 g CO2 per page load
Images 464.7 KiB 75%
JavaScript 85.5 KiB 14%
Fonts 34.7 KiB 6%
CSS 20.4 KiB 3%
Other 7.1 KiB 1%
HTML 7.0 KiB 1%
Other 3.3 KiB 1%
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
Info::
All images are well-optimized
1 images 465 KB
0 oversized -0 KB
1 legacy format
0 missing dimensions CLS risk
A+
JS Execution Cost
No JS execution data
PASS
No JS execution data
Info::
No significant JS execution detected

Main Thread Breakdown

Script Evaluation 40% Other 29% Style & Layout 16% Script Parsing & Compilation 7% Rendering 5% Parse HTML & CSS 4%
A+
Font Loading
2 fonts (35 KB)
PASS
2 fonts (35 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

35 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 497 ms LCP 937 mshttps://assets.nhs.uk/fonts/FrutigerLTW01-55Roman.woff2FrutigerLTW01-55Roman.w... https://assets.nhs.uk/fonts/FrutigerLTW01-55Roman.woff2 — 17.4 KiB — 0 ms — font-display: swaphttps://assets.nhs.uk/fonts/FrutigerLTW01-65Bold.woff2FrutigerLTW01-65Bold.woff2 https://assets.nhs.uk/fonts/FrutigerLTW01-65Bold.woff2 — 17.3 KiB — 0 ms — font-display: swap
FrutigerLTW01-55Roman.w... woff2 swap
Size 17 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
FrutigerLTW01-65Bold.woff2 woff2 swap
Size 17 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+
JS Bundles
4 scripts, 0 KB unused
PASS
4 scripts, 0 KB unused
0 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.nhs.uk/static/nhsuk/js/main.bd1962aa3fa4.js46 KB—✓1st
https://www.nhsapp.service.nhs.uk/js/v2/nhsapp.js1 KB—✓3rd
https://assets.nhs.uk/scripts/cookie-consent.js36 KB—✓3rd
https://assets.nhs.uk/scripts/login.js2 KB—✓3rd
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
HTTP Caching
max-age=5 (5 seconds)
PASS
max-age=5 (5 seconds)
Info::
Cache-Control header is set
Got: max-age=5
Info::
Effective TTL: 5 seconds (max-age=5)
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

max-age=5

DirectiveValueMeaning
max-age5Cache for 5 seconds
Effective TTL: 5 seconds
Network Waterfall
13 requests over 0ms
INFO

Performance analysis not available for this result.

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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