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https://england.nhs.uk

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
70
GRADE
C
FIX
6
REVIEW
2
PASS
7
INFO
2

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

Mobile Desktop
23
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
91
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.

4.90 s

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

16.34 s

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

706 ms

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

0.538

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

5.16 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.

18.04 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
17
7 PASS 2 REVIEW 6 FIX
D
Page Weight Budget
Action
2.4 MB transferred, 47 requests
FIX
2.4 MB transferred, 47 requests
Info::
Page weighs 4.8 MB (2.4 MB transferred)
Warning::
JavaScript is 1.5 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.5 MB
Info::
CSS is 254 KB — consider purging unused styles
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
Got: 254 KB
Info::
47 HTTP requests
Info::
Estimated 0.51 g CO2 per page load
2.4 MB / 2.4 MB budget
2.4 MB transferred
47 requests
0.51 g CO2 per page load
JavaScript 1.5 MiB 63%
Images 584.0 KiB 24%
CSS 254.1 KiB 10%
HTML 39.6 KiB 2%
Fonts 33.9 KiB 1%
Other 4.5 KiB 0%
Other 2.7 KiB 0%
Other 568 B 0%
0 2.4 MB 4.9 MB
Approaching limit

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

Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.

Why this matters

CSS bundle is large — purge unused styles (PurgeCSS, Tailwind JIT) to reduce CSS payload.

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 (2.4 MiB of 2.4 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
JS Execution Cost
Action
4584ms total JS execution
FIX
4584ms total JS execution
Warning::
https://www.gstatic.com/recaptcha/releases/gTpTIWh...: 1764ms CPU time
Warning::
https://www.england.nhs.uk/: 802ms CPU time
Warning::
Unattributable: 604ms CPU time
Warning::
https://www.googletagmanager.com/gtag/js?id=G-T33B...: 400ms CPU time
Warning::
https://www.england.nhs.uk/wp-content/themes/nhsen...: 318ms CPU time
Warning::
Third-party scripts: 4584ms (100% of total)

Main Thread Breakdown

Script Evaluation 59% Other 20% Script Parsing & Compilation 8% Style & Layout 6%
ScriptTotalScriptingParse/CompileParty
https://www.gstatic.com/recaptcha/releases/gTpTIWhbKpxADzTzkcabhXN4/recaptcha__en.js1764ms1554ms150ms3rd
https://www.england.nhs.uk/802ms20ms6ms3rd
Unattributable604ms25ms0ms3rd
https://www.googletagmanager.com/gtag/js?id=G-T33BJYG3P5&cx=c&gtm=4e64k0h2400ms320ms77ms3rd
https://www.england.nhs.uk/wp-content/themes/nhsengland/static/main-169b0c9c73c3b1f8d223e11703b65e952583f3fa.min.js?ver=6.9.4318ms239ms58ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-N5N4ZJ261ms193ms66ms3rd
https://www.england.nhs.uk/wp-content/themes/nhsengland/static/lib/jquery.min.js?ver=6.9.4164ms116ms16ms3rd
https://cc.cdn.civiccomputing.com/8/cookieControl-8.x.min.js?ver=6.9.4152ms137ms8ms3rd
https://www.england.nhs.uk/wp-content/plugins/page-links-to/dist/new-tab.js?ver=3.3.764ms56ms8ms3rd
https://www.england.nhs.uk/wp-content/themes/nhsengland/static/lib/modernizr.min.js?ver=6.9.454ms33ms2ms3rd
F
JS Bundles
Action
19 scripts, 921 KB unused
FIX
19 scripts, 921 KB unused
Warning::
https://www.england.nhs.uk/wp-content/themes/nhsen...: 269 KB unused (87%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.gstatic.com/recaptcha/releases/gTpTIWh...: 156 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.gstatic.com/recaptcha/releases/gTpTIWh...: 156 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.gstatic.com/recaptcha/releases/gTpTIWh...: 156 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-N5N...: 70 KB unused (52%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 921 KB
921 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.england.nhs.uk/wp-content/themes/nhsengland/static/main-169b0c9c73c3b1f8d223e11703b65e952583f3fa.min.js?ver=6.9.4312 KB269 KB (87%)✓3rd
https://www.gstatic.com/recaptcha/releases/gTpTIWhbKpxADzTzkcabhXN4/recaptcha__en.js0 KB156 KB (43%)✓3rd
https://www.gstatic.com/recaptcha/releases/gTpTIWhbKpxADzTzkcabhXN4/recaptcha__en.js362 KB156 KB (43%)✓3rd
https://www.gstatic.com/recaptcha/releases/gTpTIWhbKpxADzTzkcabhXN4/recaptcha__en.js362 KB156 KB (43%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-N5N4ZJ133 KB70 KB (52%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-T33BJYG3P5&cx=c&gtm=4e64k0h2153 KB63 KB (41%)✓3rd
https://www.england.nhs.uk/wp-content/themes/nhsengland/static/lib/jquery.min.js?ver=6.9.495 KB52 KB (54%)✓3rd
https://www.england.nhs.uk/wp-includes/js/dist/i18n.min.js?ver=c26c3dc7bed3667933755 KB—✓3rd
https://www.england.nhs.uk/wp-content/plugins/dxw-comment-length-limiter/assets/dxw-comment-length-limiter.js?ver=6.9.41 KB—✓3rd
https://www.england.nhs.uk/wp-content/plugins/page-links-to/dist/new-tab.js?ver=3.3.734 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
Page Weight Inventory
Action
47 resources · 2.4 MB · 921 KB savings available
FIX
47 resources · 2.4 MB · 921 KB savings available
Warning::
Page weight 1.4 MB over 1MB target
Got: 2.4 MB Expected: ≤ 1 MB
Info::
~921 KB of savings available
Warning::
46 third-party resources (100% of weight)
Info::
4 resources over 200KB
47 resources · 2.4 MiB · 46 third-party 1.4 MiB over 1MB target
JavaScript 63% · 1.5 MiB
Image 24% · 588.5 KiB
CSS 10% · 254.1 KiB
Document 2% · 39.7 KiB
Font 1% · 33.9 KiB
Other 0% · 3.2 KiB

~921.1 KiB of savings available

Remove unused JavaScript: 921.1 KiB
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
12 images, 0 KB saveable
REVIEW
12 images, 0 KB saveable
Warning::
https://www.england.nhs.uk/wp-content/themes/nhsen... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.england.nhs.uk/wp-content/uploads/2026... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.england.nhs.uk/wp-content/uploads/2025... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.england.nhs.uk/wp-content/uploads/2023... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.england.nhs.uk/wp-content/themes/nhsen... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
12 images 584 KB
0 oversized -0 KB
12 legacy format
5 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

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
1 fonts (34 KB)
PASS
1 fonts (34 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

34 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 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s 14.0 s 16.0 s FCP 4.9 s LCP 16.3 shttps://fonts.gstatic.com/s/roboto/v48/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2KFO7CnqEu92Fr1ME7kSn66a... https://fonts.gstatic.com/s/roboto/v48/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2 — 33.9 KiB — 17 ms — font-display: swap
KFO7CnqEu92Fr1ME7kSn66a... woff2 swap
Size 34 KB
Load time 17 ms
Start 2.2 s
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
2 hints, 0 missing preconnects
PASS
2 hints, 0 missing preconnects
Info::
Page uses 2 resource hint(s)

Current Resource Hints

preconnect
—
preload
—
dns-prefetch
2
prefetch
—

2 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
47 requests over 3360ms
INFO
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 FCP 4.9 s LCP 16.3 shttps://england.nhs.uk// https://england.nhs.uk/ — 301 — 82 B — 76 ms — h2https://www.england.nhs.uk/www.england.nhs.uk/ https://www.england.nhs.uk/ — 200 — 12.1 KiB — 1.1 s — h3https://www.england.nhs.uk/wp-content/plugins/contact-form-7/includes/css/styles.css?ver=6.1.5www.england.nhs.uk/wp-content/plugi... https://www.england.nhs.uk/wp-content/plugins/contact-form-7/includes/css/styles.css?ver=6.1.5 — 200 — 3.2 KiB — 16 ms — h3https://www.england.nhs.uk/wp-content/plugins/elasticpress/dist/css/general-styles.css?ver=66295efe92a630617c00www.england.nhs.uk/wp-content/plugi... https://www.england.nhs.uk/wp-content/plugins/elasticpress/dist/css/general-styles.css?ver=66295efe92a630617c00 — 200 — 2.3 KiB — 39 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static//lib/jquery-ui/themes/smoothness/jquery-ui.css?ver=6.9.4www.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static//lib/jquery-ui/themes/smoothness/jquery-ui.css?ver=6.9.4 — 200 — 36.0 KiB — 19 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/main-1fcbc37307c8dafd58a8e33776df7af78c61fe61.min.css?ver=6.9.4www.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/main-1fcbc37307c8dafd58a8e33776df7af78c61fe61.min.css?ver=6.9.4 — 200 — 167.6 KiB — 56 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/lib/jquery.min.js?ver=6.9.4www.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/lib/jquery.min.js?ver=6.9.4 — 200 — 95.2 KiB — 48 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/lib/modernizr.min.js?ver=6.9.4www.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/lib/modernizr.min.js?ver=6.9.4 — 200 — 9.9 KiB — 32 ms — h3https://cc.cdn.civiccomputing.com/8/cookieControl-8.x.min.js?ver=6.9.4cc.cdn.civiccomputing.com/8/cookieC... https://cc.cdn.civiccomputing.com/8/cookieControl-8.x.min.js?ver=6.9.4 — 200 — 13.8 KiB — 49 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/nhs-england-white.svgwww.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/nhs-england-white.svg — 200 — 2.4 KiB — 32 ms — h3https://www.england.nhs.uk/wp-content/uploads/2026/02/national-cancer-plan-final-image.jpgwww.england.nhs.uk/wp-content/uploa... https://www.england.nhs.uk/wp-content/uploads/2026/02/national-cancer-plan-final-image.jpg — 200 — 434.1 KiB — 62 ms — h3https://www.england.nhs.uk/wp-content/uploads/2025/07/10-year-health-plan-image-e1751533527615.pngwww.england.nhs.uk/wp-content/uploa... https://www.england.nhs.uk/wp-content/uploads/2025/07/10-year-health-plan-image-e1751533527615.png — 200 — 67.6 KiB — 26 ms — h3https://fast.fonts.net/t/1.css?apiType=css&projectid=df8395a8-1825-40a2-9d42-2a3c3e11b0befast.fonts.net/t/1.css?apiType=css&... https://fast.fonts.net/t/1.css?apiType=css&projectid=df8395a8-1825-40a2-9d42-2a3c3e11b0be — 200 — 638 B — 41 ms — h2https://www.england.nhs.uk/wp-content/uploads/2023/11/fdp-homepage.jpgwww.england.nhs.uk/wp-content/uploa... https://www.england.nhs.uk/wp-content/uploads/2023/11/fdp-homepage.jpg — 200 — 38.2 KiB — 19 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/nhs-uk-logo.svgwww.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/nhs-uk-logo.svg — 200 — 1.9 KiB — 19 ms — h3https://www.england.nhs.uk/wp-includes/js/dist/hooks.min.js?ver=dd5603f07f9220ed27f1www.england.nhs.uk/wp-includes/js/d... https://www.england.nhs.uk/wp-includes/js/dist/hooks.min.js?ver=dd5603f07f9220ed27f1 — 200 — 5.8 KiB — 16 ms — h3https://www.england.nhs.uk/wp-includes/js/dist/i18n.min.js?ver=c26c3dc7bed366793375www.england.nhs.uk/wp-includes/js/d... https://www.england.nhs.uk/wp-includes/js/dist/i18n.min.js?ver=c26c3dc7bed366793375 — 200 — 5.5 KiB — 15 ms — h3https://www.england.nhs.uk/wp-content/plugins/contact-form-7/includes/swv/js/index.js?ver=6.1.5www.england.nhs.uk/wp-content/plugi... https://www.england.nhs.uk/wp-content/plugins/contact-form-7/includes/swv/js/index.js?ver=6.1.5 — 200 — 12.5 KiB — 18 ms — h3https://www.england.nhs.uk/wp-content/plugins/contact-form-7/includes/js/index.js?ver=6.1.5www.england.nhs.uk/wp-content/plugi... https://www.england.nhs.uk/wp-content/plugins/contact-form-7/includes/js/index.js?ver=6.1.5 — 200 — 13.4 KiB — 17 ms — h3https://www.england.nhs.uk/wp-content/plugins/dxw-comment-length-limiter/assets/dxw-comment-length-limiter.js?ver=6.9.4www.england.nhs.uk/wp-content/plugi... https://www.england.nhs.uk/wp-content/plugins/dxw-comment-length-limiter/assets/dxw-comment-length-limiter.js?ver=6.9.4 — 200 — 1.0 KiB — 19 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/main-169b0c9c73c3b1f8d223e11703b65e952583f3fa.min.js?ver=6.9.4www.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/main-169b0c9c73c3b1f8d223e11703b65e952583f3fa.min.js?ver=6.9.4 — 200 — 311.7 KiB — 75 ms — h3https://www.england.nhs.uk/wp-content/plugins/page-links-to/dist/new-tab.js?ver=3.3.7www.england.nhs.uk/wp-content/plugi... https://www.england.nhs.uk/wp-content/plugins/page-links-to/dist/new-tab.js?ver=3.3.7 — 200 — 33.9 KiB — 30 ms — h3https://www.google.com/recaptcha/api.js?render=6Ld9JegkAAAAAEzna4HCHXBNyzb5k82ivMDZLstF&ver=3.0www.google.com/recaptcha/api.js?ren... https://www.google.com/recaptcha/api.js?render=6Ld9JegkAAAAAEzna4HCHXBNyzb5k82ivMDZLstF&ver=3.0 — 200 — 1.0 KiB — 41 ms — h3https://www.england.nhs.uk/wp-includes/js/dist/vendor/wp-polyfill.min.js?ver=3.15.0www.england.nhs.uk/wp-includes/js/d... https://www.england.nhs.uk/wp-includes/js/dist/vendor/wp-polyfill.min.js?ver=3.15.0 — 200 — 33.0 KiB — 46 ms — h3https://www.england.nhs.uk/wp-content/plugins/contact-form-7/modules/recaptcha/index.js?ver=6.1.5www.england.nhs.uk/wp-content/plugi... https://www.england.nhs.uk/wp-content/plugins/contact-form-7/modules/recaptcha/index.js?ver=6.1.5 — 200 — 1.2 KiB — 73 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/print-fe4e4682bcb96cc3674bd9e62072e3d81c0553ab.min.css?ver=6.9.4www.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/print-fe4e4682bcb96cc3674bd9e62072e3d81c0553ab.min.css?ver=6.9.4 — 200 — 2.3 KiB — 41 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/social-media-icons/bulletin.svgwww.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/social-media-icons/bulletin.svg — 200 — 6.3 KiB — 29 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/social-media-icons/twitter.svgwww.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/social-media-icons/twitter.svg — 200 — 822 B — 31 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/social-media-icons/facebook.svgwww.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/social-media-icons/facebook.svg — 200 — 12.3 KiB — 33 ms — h3https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/social-media-icons/instagram.svgwww.england.nhs.uk/wp-content/theme... https://www.england.nhs.uk/wp-content/themes/nhsengland/static/img/social-media-icons/instagram.svg — 200 — 15.4 KiB — 33 ms — h3
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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-party 4584ms · 763KB · £48/mo
www.gstatic.com
Other
Costly
Execution 1764ms
Transfer 0 KB
Unused 43%
Monthly Cost £18/mo
www.england.nhs.uk
Other
Costly
Execution 802ms
Transfer 12 KB
Monthly Cost £8/mo
Unattributable
Other
Costly
Execution 604ms
Transfer 0 KB
Monthly Cost £6/mo
Google Tag Manager
Tag Manager
Costly
Execution 400ms
Transfer 153 KB
Unused 41%
Monthly Cost £4/mo
www.england.nhs.uk
Other
Costly
Execution 318ms
Transfer 312 KB
Unused 87%
Monthly Cost £3/mo
Google Tag Manager
Tag Manager
Costly
Execution 261ms
Transfer 133 KB
Unused 52%
Monthly Cost £3/mo
www.england.nhs.uk
Other
Optional
Execution 164ms
Transfer 95 KB
Unused 54%
Monthly Cost £2/mo
cc.cdn.civiccomputing.com
Other
Optional
Execution 152ms
Transfer 14 KB
Monthly Cost £2/mo
www.england.nhs.uk
Other
Optional
Execution 64ms
Transfer 34 KB
Monthly Cost £1/mo
www.england.nhs.uk
Other
Optional
Execution 54ms
Transfer 10 KB
Monthly Cost £1/mo

These scripts may cost more than they're worth

  • www.gstatic.com adds 1764ms and costs ~£18/month
  • www.england.nhs.uk adds 802ms and costs ~£8/month
  • Unattributable adds 604ms and costs ~£6/month
  • Google Tag Manager adds 400ms and costs ~£4/month
  • www.england.nhs.uk adds 318ms and costs ~£3/month
  • Google Tag Manager adds 261ms 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

www.gstatic.com takes 1764ms 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.england.nhs.uk takes 802ms 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 604ms 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 400ms 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.england.nhs.uk takes 318ms 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

87% of www.england.nhs.uk'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

Google Tag Manager takes 261ms 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 Google Tag Manager'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

54% of www.england.nhs.uk'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

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