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https://bhf.org.uk

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
66
GRADE
D
FIX
6
REVIEW
1
PASS
8
INFO
2

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

Mobile Desktop
21
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.

2.91 s

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

6.15 s

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

2.80 s

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

0.354

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

6.12 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.

16.71 s

Page Load Progression

620 ms
1.2 s
1.9 s
2.5 s
3.1 s
3.7 s
4.3 s
5.0 s
Checks
17
8 PASS 1 REVIEW 6 FIX
F
Page Weight Budget
Action
9.2 MB transferred, 52 requests
FIX
9.2 MB transferred, 52 requests
Critical::
Page weighs 17.4 MB (9.2 MB transferred)
Warning::
JavaScript is 1.8 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.8 MB
Info::
CSS is 225 KB — consider purging unused styles
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
Got: 225 KB
Info::
52 HTTP requests
Info::
Estimated 1.9 g CO2 per page load
9.2 MB / 2.4 MB budget
9.2 MB transferred
52 requests
1.9 g CO2 per page load
Other 3.3 MiB 36%
Other 3.3 MiB 36%
JavaScript 1.8 MiB 20%
Images 426.9 KiB 5%
CSS 225.4 KiB 2%
Fonts 59.7 KiB 1%
Other 58.6 KiB 1%
HTML 27.0 KiB 0%
Other 11.4 KiB 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

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 (9.2 MiB of 9.2 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
JS Execution Cost
Action
7562ms total JS execution
FIX
7562ms total JS execution
Warning::
https://www.bhf.org.uk/assets/js/app-mvc.js?v=6snW...: 1731ms CPU time
Warning::
Unattributable: 1538ms CPU time
Warning::
https://www.bhf.org.uk/: 928ms CPU time
Warning::
https://www.bhf.org.uk/metrics/: 722ms CPU time
Warning::
https://cdn.cookielaw.org/scripttemplates/202601.2...: 477ms CPU time
Warning::
Third-party scripts: 7562ms (100% of total)

Main Thread Breakdown

Script Evaluation 49% Other 20% Style & Layout 14% Script Parsing & Compilation 10% Garbage Collection 3%
ScriptTotalScriptingParse/CompileParty
https://www.bhf.org.uk/assets/js/app-mvc.js?v=6snWwysaXYUPvFVemwjQnExtiSaz8ZpjHfBEdtahKaA=1731ms1215ms99ms3rd
Unattributable1538ms144ms0ms3rd
https://www.bhf.org.uk/928ms29ms6ms3rd
https://www.bhf.org.uk/metrics/722ms591ms108ms3rd
https://cdn.cookielaw.org/scripttemplates/202601.2.0/otBannerSdk.js477ms329ms67ms3rd
https://www.bhf.org.uk/metrics/?id=G-L1TRS9RE0M&cx=c&gtm=4e64k0388ms313ms72ms3rd
https://www.bhf.org.uk/assets/js/custom-mvc.js?v=aegVAHwzwuFyfcn0myoprLYXoncouBCN2rCroqlljYw=362ms207ms20ms3rd
https://www.bhf.org.uk/metrics/?id=DC-8455068&cx=c&gtm=4e64k0224ms159ms64ms3rd
https://www.bhf.org.uk/metrics/?id=AW-1051090846&cx=c&gtm=4e64k0196ms143ms51ms3rd
https://www.bhf.org.uk/metrics/?id=AW-882124424&cx=c&gtm=4e64k0191ms144ms45ms3rd

Showing top 10 of 16 scripts

F
JS Bundles
Action
14 scripts, 1.0 MB unused
FIX
14 scripts, 1.0 MB unused
Warning::
https://www.bhf.org.uk/assets/js/app-mvc.js?v=6snW...: 172 KB unused (72%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-M3W...: 97 KB unused (46%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.bhf.org.uk/metrics/?id=G-L1TRS9RE0M&cx...: 90 KB unused (49%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.bhf.org.uk/assets/js/forms-mvc.js?v=ok...: 85 KB unused (90%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.bhf.org.uk/metrics/gtd?id=AW-AW-105109...: 84 KB unused (60%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 1.0 MB
1033 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.bhf.org.uk/assets/js/app-mvc.js?v=6snWwysaXYUPvFVemwjQnExtiSaz8ZpjHfBEdtahKaA=248 KB172 KB (72%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-M3WB36&gtm_auth=Ihs5a3k1yY9t8Y2x_DMt1w&gtm_preview=env-140&gtm_cookies_win=x212 KB97 KB (46%)✓3rd
https://www.bhf.org.uk/metrics/?id=G-L1TRS9RE0M&cx=c&gtm=4e64k0183 KB90 KB (49%)✓3rd
https://www.bhf.org.uk/assets/js/forms-mvc.js?v=okVqgsXr9CmUY5Nr0pHPolevl50Naydl0skP7gyjMzE=104 KB85 KB (90%)✓3rd
https://www.bhf.org.uk/metrics/gtd?id=AW-AW-1051090846&cx=c&gtm=4e64k0140 KB84 KB (60%)✓3rd
https://www.bhf.org.uk/metrics/gtd?id=AW-AW-882124424&cx=c&gtm=4e64k0140 KB84 KB (60%)✓3rd
https://www.bhf.org.uk/metrics/?id=AW-1051090846&cx=c&gtm=4e64k0142 KB83 KB (59%)✓3rd
https://www.bhf.org.uk/metrics/?id=AW-882124424&cx=c&gtm=4e64k0140 KB82 KB (59%)✓3rd
https://www.bhf.org.uk/metrics/?id=DC-8455068&cx=c&gtm=4e64k0137 KB79 KB (58%)✓3rd
https://www.bhf.org.uk/metrics/215 KB72 KB (34%)✓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
52 resources · 9.2 MB · 1.0 MB savings available
FIX
52 resources · 9.2 MB · 1.0 MB savings available
Warning::
Page weight 8.2 MB over 1MB target
Got: 9.2 MB Expected: ≤ 1 MB
Info::
~1.0 MB of savings available
Warning::
51 third-party resources (100% of weight)
Info::
6 resources over 200KB
52 resources · 9.2 MiB · 51 third-party 8.2 MiB over 1MB target
Media 71% · 6.6 MiB
JavaScript 20% · 1.8 MiB
Image 5% · 438.3 KiB
CSS 2% · 230.1 KiB
Font 1% · 59.7 KiB
Other 1% · 56.1 KiB
Document 0% · 27.5 KiB

~1.0 MiB of savings available

Remove unused JavaScript: 1.0 MiB
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
19 images, 0 KB saveable
REVIEW
19 images, 0 KB saveable
Warning::
https://www.bhf.org.uk/-/media/system/logo-white.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.bhf.org.uk/assets/img/BHF-logo.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.bhf.org.uk/-/media/system/fr-white.svg... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
19 images 427 KB
0 oversized -0 KB
12 legacy format
3 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

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 (60 KB)
PASS
2 fonts (60 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

60 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 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s 6.0 s FCP 2.9 s LCP 6.1 shttps://www.bhf.org.uk/assets/fonts/bhf_icons.woff2?v=dcb19ae2ea5c52ddcb7e88153f4674d61a75f6db831fde8e25e7c20838a568bdbhf_icons.woff2 https://www.bhf.org.uk/assets/fonts/bhf_icons.woff2?v=dcb19ae2ea5c52ddcb7e88153f4674d61a75f6db831fde8e25e7c20838a568bd — 19.9 KiB — 38 ms — font-display: swaphttps://www.bhf.org.uk/assets/fonts/BHFBeats-Bold.woffBHFBeats-Bold.woff https://www.bhf.org.uk/assets/fonts/BHFBeats-Bold.woff — 39.9 KiB — 39 ms — font-display: swap
bhf_icons.woff2 woff2 swap
Size 20 KB
Load time 38 ms
Start 620 ms
Risk FOUT — text flashes from fallback to web font
BHFBeats-Bold.woff woff swap
Size 40 KB
Load time 39 ms
Start 620 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)

Fixing the unchecked items could save ~12 KB and ~24 ms

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+
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
A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

Network Waterfall
52 requests over 2633ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s 6.0 s FCP 2.9 s LCP 6.1 shttps://bhf.org.uk// https://bhf.org.uk/ — 301 — 421 B — 45 ms — h2https://www.bhf.org.uk/www.bhf.org.uk/ https://www.bhf.org.uk/ — 200 — 27.0 KiB — 324 ms — h2https://www.bhf.org.uk/assets/css/styles-backend.css?v=aYd01jzxindQL2gGxY2u6xNm8bKx9V16CWeVuzbqNLY=www.bhf.org.uk/assets/css/styles-ba... https://www.bhf.org.uk/assets/css/styles-backend.css?v=aYd01jzxindQL2gGxY2u6xNm8bKx9V16CWeVuzbqNLY= — 200 — 10.1 KiB — 37 ms — h2https://www.bhf.org.uk/assets/css/styles-with-grid-system.css?v=Ww26qMeXN1L7WZjmzjSKlfZVTXqAuhqzhK3tUUO+YVU=www.bhf.org.uk/assets/css/styles-wi... https://www.bhf.org.uk/assets/css/styles-with-grid-system.css?v=Ww26qMeXN1L7WZjmzjSKlfZVTXqAuhqzhK3tUUO+YVU= — 200 — 204.8 KiB — 43 ms — h2https://www.bhf.org.uk/assets/fonts/bhf_icons.css?v=5fKB8Be4f6s0/BiWpZ2kOkKi3Ua4DV/WXKnZBZydyGQ=www.bhf.org.uk/assets/fonts/bhf_ico... https://www.bhf.org.uk/assets/fonts/bhf_icons.css?v=5fKB8Be4f6s0/BiWpZ2kOkKi3Ua4DV/WXKnZBZydyGQ= — 200 — 10.6 KiB — 39 ms — h2https://www.bhf.org.uk/assets/img/BHF-logo.svgwww.bhf.org.uk/assets/img/BHF-logo.... https://www.bhf.org.uk/assets/img/BHF-logo.svg — 200 — 10.3 KiB — 39 ms — h2https://www.bhf.org.uk/assets/img/BHF-logo-desktop.svgwww.bhf.org.uk/assets/img/BHF-logo-... https://www.bhf.org.uk/assets/img/BHF-logo-desktop.svg — 200 — 13.1 KiB — 39 ms — h2https://www.bhf.org.uk/-/media/images/nav-promo-panels/volunteer-in-our-shops_group-of-volunteers-400x225px.jpg?rev=a737b12ce7f6436b8272217f09a73730www.bhf.org.uk/-/media/images/nav-p... https://www.bhf.org.uk/-/media/images/nav-promo-panels/volunteer-in-our-shops_group-of-volunteers-400x225px.jpg?rev=a737b12ce7f6436b8272217f09a73730 — 200 — 34.7 KiB — 24 ms — h2https://www.bhf.org.uk/-/media/images/nav-promo-panels/heartstatistics-400x225.jpg?rev=0198052ab398483f855242de633fd425www.bhf.org.uk/-/media/images/nav-p... https://www.bhf.org.uk/-/media/images/nav-promo-panels/heartstatistics-400x225.jpg?rev=0198052ab398483f855242de633fd425 — 200 — 24.2 KiB — 18 ms — h2https://www.bhf.org.uk/-/media/images/donate/category-page/lottery-raffle-faqsv2-600x450.jpg?rev=3ba70ec240864d67944e1192def08f63www.bhf.org.uk/-/media/images/donat... https://www.bhf.org.uk/-/media/images/donate/category-page/lottery-raffle-faqsv2-600x450.jpg?rev=3ba70ec240864d67944e1192def08f63 — 200 — 37.5 KiB — 16 ms — h2https://www.bhf.org.uk/assets/js/custom-mvc.js?v=aegVAHwzwuFyfcn0myoprLYXoncouBCN2rCroqlljYw=www.bhf.org.uk/assets/js/custom-mvc... https://www.bhf.org.uk/assets/js/custom-mvc.js?v=aegVAHwzwuFyfcn0myoprLYXoncouBCN2rCroqlljYw= — 200 — 69.6 KiB — 34 ms — h2https://www.bhf.org.uk/assets/js/app-mvc.js?v=6snWwysaXYUPvFVemwjQnExtiSaz8ZpjHfBEdtahKaA=www.bhf.org.uk/assets/js/app-mvc.js... https://www.bhf.org.uk/assets/js/app-mvc.js?v=6snWwysaXYUPvFVemwjQnExtiSaz8ZpjHfBEdtahKaA= — 200 — 247.7 KiB — 55 ms — h2https://www.bhf.org.uk/assets/js/forms-mvc.js?v=okVqgsXr9CmUY5Nr0pHPolevl50Naydl0skP7gyjMzE=www.bhf.org.uk/assets/js/forms-mvc.... https://www.bhf.org.uk/assets/js/forms-mvc.js?v=okVqgsXr9CmUY5Nr0pHPolevl50Naydl0skP7gyjMzE= — 200 — 104.5 KiB — 37 ms — h2https://www.bhf.org.uk/-/media/images/keep-us-beating/bhf-home-keep-us-beating-video-thumbnail-banner-1600-900px.jpg?rev=af7c7ed8a5e64cbdb9aaa076eb51c2ef&la=en&h=900&w=1600&hash=0B79CB3E8A9AD3F623665F9A42A7A4AFwww.bhf.org.uk/-/media/images/keep-... https://www.bhf.org.uk/-/media/images/keep-us-beating/bhf-home-keep-us-beating-video-thumbnail-banner-1600-900px.jpg?rev=af7c7ed8a5e64cbdb9aaa076eb51c2ef&la=en&h=900&w=1600&hash=0B79CB3E8A9AD3F623665F9A42A7A4AF — 200 — 51.8 KiB — 43 ms — h2https://www.bhf.org.uk/-/media/system/logo-white.svg?rev=f07c00ef8c1c41bcb2458bc592052b43&la=en&hash=BBA651047E4F09B23E0E4345D6031A2Dwww.bhf.org.uk/-/media/system/logo-... https://www.bhf.org.uk/-/media/system/logo-white.svg?rev=f07c00ef8c1c41bcb2458bc592052b43&la=en&hash=BBA651047E4F09B23E0E4345D6031A2D — 200 — 12.1 KiB — 46 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-M3WB36&gtm_auth=Ihs5a3k1yY9t8Y2x_DMt1w&gtm_preview=env-140&gtm_cookies_win=xwww.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-M3WB36&gtm_auth=Ihs5a3k1yY9t8Y2x_DMt1w&gtm_preview=env-140&gtm_cookies_win=x — 200 — 211.5 KiB — 279 ms — h2https://www.bhf.org.uk/-/media/system/fr-white.svg?rev=a8b55cd0fd5744c69e76938d58165e56&la=en&hash=95F0485EB6CFB6092646692F8C67F121www.bhf.org.uk/-/media/system/fr-wh... https://www.bhf.org.uk/-/media/system/fr-white.svg?rev=a8b55cd0fd5744c69e76938d58165e56&la=en&hash=95F0485EB6CFB6092646692F8C67F121 — 200 — 12.9 KiB — 36 ms — h2https://www.bhf.org.uk/metrics/www.bhf.org.uk/metrics/ https://www.bhf.org.uk/metrics/ — 200 — 215.4 KiB — 555 ms — h2https://www.bhf.org.uk/-/media/images/keep-us-beating/keep-us-beating-banner-video-16x9-compressed.mp4?rev=d7304a16f0b54e58a3e53833acd96771www.bhf.org.uk/-/media/images/keep-... https://www.bhf.org.uk/-/media/images/keep-us-beating/keep-us-beating-banner-video-16x9-compressed.mp4?rev=d7304a16f0b54e58a3e53833acd96771 — 206 — 9.5 KiB — 273 ms — h2https://www.bhf.org.uk/assets/img/svgs/hero-banner-horizontal-curv.svgwww.bhf.org.uk/assets/img/svgs/hero... https://www.bhf.org.uk/assets/img/svgs/hero-banner-horizontal-curv.svg — 200 — 9.5 KiB — 48 ms — h2https://www.bhf.org.uk/assets/img/icons/grey-arrow.svgwww.bhf.org.uk/assets/img/icons/gre... https://www.bhf.org.uk/assets/img/icons/grey-arrow.svg — 200 — 9.5 KiB — 50 ms — h2https://www.bhf.org.uk/assets/img/icons/arrow-left-red.svgwww.bhf.org.uk/assets/img/icons/arr... https://www.bhf.org.uk/assets/img/icons/arrow-left-red.svg — 200 — 9.5 KiB — 44 ms — h2https://www.bhf.org.uk/assets/img/icons/arrow-right-red.svgwww.bhf.org.uk/assets/img/icons/arr... https://www.bhf.org.uk/assets/img/icons/arrow-right-red.svg — 200 — 9.5 KiB — 39 ms — h2https://www.bhf.org.uk/assets/fonts/bhf_icons.woff2?v=dcb19ae2ea5c52ddcb7e88153f4674d61a75f6db831fde8e25e7c20838a568bdwww.bhf.org.uk/assets/fonts/bhf_ico... https://www.bhf.org.uk/assets/fonts/bhf_icons.woff2?v=dcb19ae2ea5c52ddcb7e88153f4674d61a75f6db831fde8e25e7c20838a568bd — 200 — 19.9 KiB — 38 ms — h2https://www.bhf.org.uk/assets/fonts/BHFBeats-Bold.woffwww.bhf.org.uk/assets/fonts/BHFBeat... https://www.bhf.org.uk/assets/fonts/BHFBeats-Bold.woff — 200 — 39.9 KiB — 39 ms — h2https://www.bhf.org.uk/-/media/images/keep-us-beating/keep-us-beating-banner-video-16x9-compressed.mp4?rev=d7304a16f0b54e58a3e53833acd96771www.bhf.org.uk/-/media/images/keep-... https://www.bhf.org.uk/-/media/images/keep-us-beating/keep-us-beating-banner-video-16x9-compressed.mp4?rev=d7304a16f0b54e58a3e53833acd96771 — 200 — 3.3 MiB — 324 ms — h2https://www.bhf.org.uk/-/media/images/keep-us-beating/keep-us-beating-banner-video-16x9-compressed.mp4?rev=d7304a16f0b54e58a3e53833acd96771www.bhf.org.uk/-/media/images/keep-... https://www.bhf.org.uk/-/media/images/keep-us-beating/keep-us-beating-banner-video-16x9-compressed.mp4?rev=d7304a16f0b54e58a3e53833acd96771 — 200 — 3.3 MiB — 267 ms — h2https://www.bhf.org.uk/assets/img/icons/arrow-left-grey.svgwww.bhf.org.uk/assets/img/icons/arr... https://www.bhf.org.uk/assets/img/icons/arrow-left-grey.svg — 200 — 9.5 KiB — 97 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-M3WB36&gtg_health=1www.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-M3WB36&gtg_health=1 — 200 — 258 B — 61 ms — h2https://www.bhf.org.uk/metrics/?id=G-L1TRS9RE0M&cx=c&gtm=4e64k0www.bhf.org.uk/metrics/?id=G-L1TRS9... https://www.bhf.org.uk/metrics/?id=G-L1TRS9RE0M&cx=c&gtm=4e64k0 — 200 — 182.6 KiB — 428 ms — h2
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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 7562ms · 2099KB · £112/mo
www.bhf.org.uk
Other
Costly
Execution 1731ms
Transfer 248 KB
Unused 72%
Monthly Cost £26/mo
Unattributable
Other
Costly
Execution 1538ms
Transfer 0 KB
Monthly Cost £23/mo
www.bhf.org.uk
Other
Costly
Execution 928ms
Transfer 27 KB
Monthly Cost £14/mo
www.bhf.org.uk
Other
Costly
Execution 722ms
Transfer 215 KB
Unused 34%
Monthly Cost £11/mo
OneTrust
Consent
Essential
Execution 477ms
Transfer 128 KB
Unused 53%
Monthly Cost £7/mo
www.bhf.org.uk
Other
Costly
Execution 388ms
Transfer 183 KB
Unused 49%
Monthly Cost £6/mo
www.bhf.org.uk
Other
Costly
Execution 362ms
Transfer 70 KB
Unused 59%
Monthly Cost £5/mo
www.bhf.org.uk
Other
Costly
Execution 224ms
Transfer 137 KB
Unused 58%
Monthly Cost £3/mo
www.bhf.org.uk
Other
Optional
Execution 196ms
Transfer 142 KB
Unused 59%
Monthly Cost £3/mo
www.bhf.org.uk
Other
Optional
Execution 191ms
Transfer 140 KB
Unused 59%
Monthly Cost £3/mo
www.bhf.org.uk
Other
Optional
Execution 188ms
Transfer 140 KB
Unused 60%
Monthly Cost £3/mo
www.bhf.org.uk
Other
Optional
Execution 177ms
Transfer 140 KB
Unused 60%
Monthly Cost £3/mo
Google Tag Manager
Tag Manager
Optional
Execution 172ms
Transfer 212 KB
Unused 46%
Monthly Cost £3/mo
www.bhf.org.uk
Other
Optional
Execution 111ms
Transfer 205 KB
Monthly Cost £2/mo
www.bhf.org.uk
Other
Optional
Execution 87ms
Transfer 104 KB
Unused 90%
Monthly Cost £1/mo
OneTrust
Consent
Essential
Execution 70ms
Transfer 9 KB
Monthly Cost £1/mo

These scripts may cost more than they're worth

  • www.bhf.org.uk adds 1731ms and costs ~£26/month
  • Unattributable adds 1538ms and costs ~£23/month
  • www.bhf.org.uk adds 928ms and costs ~£14/month
  • www.bhf.org.uk adds 722ms and costs ~£11/month
  • www.bhf.org.uk adds 388ms and costs ~£6/month
  • www.bhf.org.uk adds 362ms and costs ~£5/month
  • www.bhf.org.uk adds 224ms 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.

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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.bhf.org.uk takes 1731ms 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

72% of www.bhf.org.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

Unattributable takes 1538ms 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.bhf.org.uk takes 928ms 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.bhf.org.uk takes 722ms 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

53% of OneTrust'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.bhf.org.uk takes 388ms 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.bhf.org.uk takes 362ms 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

59% of www.bhf.org.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

www.bhf.org.uk takes 224ms 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.bhf.org.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

59% of www.bhf.org.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

59% of www.bhf.org.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

60% of www.bhf.org.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

60% of www.bhf.org.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

90% of www.bhf.org.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

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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