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https://cancerresearchuk.org

Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
71
GRADE
C
FIX
5
REVIEW
2
PASS
6
INFO
2

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

Mobile Desktop
92
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
94
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
96
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.

827 ms

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

1.82 s

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

56 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.

827 ms

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

2.90 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
15
6 PASS 2 REVIEW 5 FIX
F
Page Weight Budget
Action
2.8 MB transferred, 55 requests
FIX
2.8 MB transferred, 55 requests
Warning::
Page weighs 6.4 MB (2.8 MB transferred)
Warning::
JavaScript is 1.7 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.7 MB
Info::
Fonts are 782 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 782 KB
Info::
55 HTTP requests
Info::
Estimated 0.59 g CO2 per page load
2.8 MB / 2.4 MB budget
2.8 MB transferred
55 requests
0.59 g CO2 per page load
JavaScript 1.7 MiB 60%
Fonts 782.0 KiB 27%
Images 249.3 KiB 9%
HTML 56.3 KiB 2%
Other 38.3 KiB 1%
CSS 10.9 KiB 0%
Other 3.6 KiB 0%
Other 42 B 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

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

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 (2.8 MiB of 2.8 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
JS Bundles
Action
27 scripts, 568 KB unused
FIX
27 scripts, 568 KB unused
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-KHM...: 78 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.cancerresearchuk.org/_next/static/chun...: 78 KB unused (45%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-5873...: 77 KB unused (46%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=AW-986...: 66 KB unused (48%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=DC-872...: 64 KB unused (49%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 568 KB
568 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtm.js?id=GTM-KHMJ7CS181 KB78 KB (43%)✓3rd
https://www.cancerresearchuk.org/_next/static/chunks/7180-be8f246206a70c65.js174 KB78 KB (45%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-58736Z2GNN&cx=c&gtm=4e64h1168 KB77 KB (46%)✓3rd
https://www.googletagmanager.com/gtag/js?id=AW-986083629&cx=c&gtm=4e64h1137 KB66 KB (48%)✓3rd
https://www.googletagmanager.com/gtag/js?id=DC-8727222&cx=c&gtm=4e64h1130 KB64 KB (49%)✓3rd
https://www.cancerresearchuk.org/_next/static/chunks/2691-38189575cf339bed.js64 KB49 KB (81%)✓3rd
https://www.cancerresearchuk.org/_next/static/chunks/7105-e8c503187482c546.js263 KB46 KB (18%)✓3rd
https://www.cancerresearchuk.org/_next/static/chunks/1377-c76d500bf8de9995.js256 KB42 KB (16%)✓3rd
https://www.cancerresearchuk.org/_next/static/chunks/7693-ddc473c47d5fbf1c.js55 KB37 KB (72%)✓3rd
https://www.cancerresearchuk.org/_next/static/chunks/4052-cc3a4da56124ab29.js43 KB31 KB (80%)✓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
55 resources · 2.8 MB · 568 KB savings available
FIX
55 resources · 2.8 MB · 568 KB savings available
Warning::
Page weight 1.8 MB over 1MB target
Got: 2.8 MB Expected: ≤ 1 MB
Info::
~568 KB of savings available
Warning::
54 third-party resources (100% of weight)
Info::
2 resources over 200KB
55 resources · 2.8 MiB · 54 third-party 1.8 MiB over 1MB target
JavaScript 60% · 1.7 MiB
Font 27% · 782.0 KiB
Image 10% · 287.5 KiB
Document 2% · 56.4 KiB
CSS 0% · 10.9 KiB
Other 0% · 3.6 KiB

~567.6 KiB of savings available

Remove unused JavaScript: 567.6 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.

B
JS Execution Cost
652ms total JS execution
REVIEW
652ms total JS execution
Info::
https://www.cancerresearchuk.org/_next/static/chun...: 168ms CPU time
Info::
https://www.cancerresearchuk.org/: 113ms CPU time
Info::
https://www.cancerresearchuk.org/_next/static/chun...: 102ms CPU time
Info::
Unattributable: 84ms CPU time
Info::
https://www.googletagmanager.com/gtm.js?id=GTM-KHM...: 66ms CPU time
Warning::
Third-party scripts: 652ms (100% of total)

Main Thread Breakdown

Script Evaluation 61% Script Parsing & Compilation 13% Other 13% Style & Layout 10%
ScriptTotalScriptingParse/CompileParty
https://www.cancerresearchuk.org/_next/static/chunks/18-f78cdf1f90d3fe0f.js168ms150ms4ms3rd
https://www.cancerresearchuk.org/113ms3ms6ms3rd
https://www.cancerresearchuk.org/_next/static/chunks/7105-e8c503187482c546.js102ms88ms13ms3rd
Unattributable84ms2ms0ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-KHMJ7CS66ms53ms12ms3rd
https://www.googletagmanager.com/gtag/js?id=AW-986083629&cx=c&gtm=4e64h164ms55ms8ms3rd
https://www.cancerresearchuk.org/_next/static/chunks/1377-c76d500bf8de9995.js57ms45ms12ms3rd
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+
Image Optimization
8 images, 0 KB saveable
PASS
8 images, 0 KB saveable
Info::
All images are well-optimized
8 images 249 KB
0 oversized -0 KB
1 legacy format
0 missing dimensions CLS risk
A+
Font Loading
10 fonts (782 KB)
PASS
10 fonts (782 KB)
Info::
10 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

10

782 KB total

Render-blocking

0

of 10

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s 1.5 s FCP 827 ms LCP 1.8 shttps://www.cancerresearchuk.org/_next/static/media/001e002f03b017c1-s.p.woff001e002f03b017c1-s.p.woff https://www.cancerresearchuk.org/_next/static/media/001e002f03b017c1-s.p.woff — 74.4 KiB — 43 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/22f59f5d5b479322-s.p.woff22f59f5d5b479322-s.p.woff https://www.cancerresearchuk.org/_next/static/media/22f59f5d5b479322-s.p.woff — 143.8 KiB — 54 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/35789c96e49e6b7f-s.p.woff35789c96e49e6b7f-s.p.woff https://www.cancerresearchuk.org/_next/static/media/35789c96e49e6b7f-s.p.woff — 72.6 KiB — 44 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/6eb962549b7dc14e-s.p.woff6eb962549b7dc14e-s.p.woff https://www.cancerresearchuk.org/_next/static/media/6eb962549b7dc14e-s.p.woff — 45.7 KiB — 42 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/72b3d441bbdb517b-s.p.woff72b3d441bbdb517b-s.p.woff https://www.cancerresearchuk.org/_next/static/media/72b3d441bbdb517b-s.p.woff — 44.8 KiB — 43 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/82b68f6f091d46c1-s.p.woff82b68f6f091d46c1-s.p.woff https://www.cancerresearchuk.org/_next/static/media/82b68f6f091d46c1-s.p.woff — 44.6 KiB — 43 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/aac452a0af5508c6-s.p.woffaac452a0af5508c6-s.p.woff https://www.cancerresearchuk.org/_next/static/media/aac452a0af5508c6-s.p.woff — 45.6 KiB — 45 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/bb3853c711608cc5-s.p.woffbb3853c711608cc5-s.p.woff https://www.cancerresearchuk.org/_next/static/media/bb3853c711608cc5-s.p.woff — 69.7 KiB — 49 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/e21fa8781a9a32b3-s.p.woffe21fa8781a9a32b3-s.p.woff https://www.cancerresearchuk.org/_next/static/media/e21fa8781a9a32b3-s.p.woff — 74.9 KiB — 54 ms — font-display: swaphttps://www.cancerresearchuk.org/_next/static/media/fb98212e27cc7064-s.p.wofffb98212e27cc7064-s.p.woff https://www.cancerresearchuk.org/_next/static/media/fb98212e27cc7064-s.p.woff — 166.0 KiB — 48 ms — font-display: swap
001e002f03b017c1-s.p.woff woff swap
Size 74 KB
Load time 43 ms
Start 106 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
22f59f5d5b479322-s.p.woff woff swap
Size 144 KB
Load time 54 ms
Start 107 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
35789c96e49e6b7f-s.p.woff woff swap
Size 73 KB
Load time 44 ms
Start 107 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
6eb962549b7dc14e-s.p.woff woff swap
Size 46 KB
Load time 42 ms
Start 107 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
72b3d441bbdb517b-s.p.woff woff swap
Size 45 KB
Load time 43 ms
Start 107 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
82b68f6f091d46c1-s.p.woff woff swap
Size 45 KB
Load time 43 ms
Start 108 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
aac452a0af5508c6-s.p.woff woff swap
Size 46 KB
Load time 45 ms
Start 108 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
bb3853c711608cc5-s.p.woff woff swap
Size 70 KB
Load time 49 ms
Start 108 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
e21fa8781a9a32b3-s.p.woff woff swap
Size 75 KB
Load time 54 ms
Start 108 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
fb98212e27cc7064-s.p.woff woff swap
Size 166 KB
Load time 48 ms
Start 108 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
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 ~389 KB and ~778 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
Network Waterfall
55 requests over 1215ms
INFO
0 ms 500 ms 1.0 s 1.5 s FCP 827 ms LCP 1.8 shttps://cancerresearchuk.org// https://cancerresearchuk.org/ — 301 — 91 B — 85 ms — h2https://www.cancerresearchuk.org/www.cancerresearchuk.org/ https://www.cancerresearchuk.org/ — 200 — 56.3 KiB — 11 ms — h2https://www.cancerresearchuk.org/_next/static/media/001e002f03b017c1-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/001e002f03b017c1-s.p.woff — 200 — 74.4 KiB — 43 ms — h2https://www.cancerresearchuk.org/_next/static/media/22f59f5d5b479322-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/22f59f5d5b479322-s.p.woff — 200 — 143.8 KiB — 54 ms — h2https://www.cancerresearchuk.org/_next/static/media/35789c96e49e6b7f-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/35789c96e49e6b7f-s.p.woff — 200 — 72.6 KiB — 44 ms — h2https://www.cancerresearchuk.org/_next/static/media/6eb962549b7dc14e-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/6eb962549b7dc14e-s.p.woff — 200 — 45.7 KiB — 42 ms — h2https://www.cancerresearchuk.org/_next/static/media/72b3d441bbdb517b-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/72b3d441bbdb517b-s.p.woff — 200 — 44.8 KiB — 43 ms — h2https://www.cancerresearchuk.org/_next/static/media/82b68f6f091d46c1-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/82b68f6f091d46c1-s.p.woff — 200 — 44.6 KiB — 43 ms — h2https://www.cancerresearchuk.org/_next/static/media/aac452a0af5508c6-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/aac452a0af5508c6-s.p.woff — 200 — 45.6 KiB — 45 ms — h2https://www.cancerresearchuk.org/_next/static/media/bb3853c711608cc5-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/bb3853c711608cc5-s.p.woff — 200 — 69.7 KiB — 49 ms — h2https://www.cancerresearchuk.org/_next/static/media/e21fa8781a9a32b3-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/e21fa8781a9a32b3-s.p.woff — 200 — 74.9 KiB — 54 ms — h2https://www.cancerresearchuk.org/_next/static/media/fb98212e27cc7064-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/fb98212e27cc7064-s.p.woff — 200 — 166.0 KiB — 48 ms — h2https://cdn.cookielaw.org/scripttemplates/otSDKStub.jscdn.cookielaw.org/scripttemplates/o... https://cdn.cookielaw.org/scripttemplates/otSDKStub.js — -1 — 0 B — 136 ms — https://www.cancerresearchuk.org/_next/static/css/c361d1f26b524758.csswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/css/c361d1f26b524758.css — 200 — 3.6 KiB — 16 ms — h2https://www.cancerresearchuk.org/_next/static/css/c682fa5ca7232dbe.csswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/css/c682fa5ca7232dbe.css — 200 — 3.4 KiB — 19 ms — h2https://www.cancerresearchuk.org/_next/static/css/761dc5ff23fcdfa0.csswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/css/761dc5ff23fcdfa0.css — 200 — 3.9 KiB — 17 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-KHMJ7CSwww.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-KHMJ7CS — 200 — 181.5 KiB — 161 ms — h2https://images.ctfassets.net/u7vsjnoopqo5/4uDzgmkufKEz5N4ef7374L/6418128c52a524c1ffad4a815f68ecee/cruk-logo.svgimages.ctfassets.net/u7vsjnoopqo5/4... https://images.ctfassets.net/u7vsjnoopqo5/4uDzgmkufKEz5N4ef7374L/6418128c52a524c1ffad4a815f68ecee/cruk-logo.svg — 200 — 6.7 KiB — 75 ms — h2https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F4KvYfwN2xheb6YkPFfL0Re%2F483d435617c31f7394ada12dbed5d7a8%2FDAT-DSC_0678.webp&w=1920&q=65www.cancerresearchuk.org/_next/imag... https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F4KvYfwN2xheb6YkPFfL0Re%2F483d435617c31f7394ada12dbed5d7a8%2FDAT-DSC_0678.webp&w=1920&q=65 — 200 — 66.7 KiB — 78 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/webpack-d18f008b72876714.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/webpack-d18f008b72876714.js — 200 — 5.7 KiB — 46 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/87c73c54-dd8d81ac9604067c.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/87c73c54-dd8d81ac9604067c.js — 200 — 57.6 KiB — 84 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/18-f78cdf1f90d3fe0f.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/18-f78cdf1f90d3fe0f.js — 200 — 48.2 KiB — 81 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/main-app-57aa1716f0d0f500.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/main-app-57aa1716f0d0f500.js — 200 — 3.8 KiB — 48 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/7180-be8f246206a70c65.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/7180-be8f246206a70c65.js — 200 — 174.1 KiB — 96 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/7105-e8c503187482c546.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/7105-e8c503187482c546.js — 200 — 262.6 KiB — 109 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/8619-0ff90b77525dda4d.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/8619-0ff90b77525dda4d.js — 200 — 14.5 KiB — 80 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/7852-beba7ef95a6f0242.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/7852-beba7ef95a6f0242.js — 200 — 8.3 KiB — 69 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/3295-faf68d8d3dc812dd.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/3295-faf68d8d3dc812dd.js — 200 — 6.4 KiB — 50 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/2691-38189575cf339bed.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/2691-38189575cf339bed.js — 200 — 63.7 KiB — 85 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/4925-3876f624fa71ddb4.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/4925-3876f624fa71ddb4.js — 200 — 7.3 KiB — 50 ms — h2
0 ms 500 ms 1.0 s 1.5 s FCP 827 ms LCP 1.8 shttps://cancerresearchuk.org// https://cancerresearchuk.org/ — 301 — 91 B — 85 ms — h2https://www.cancerresearchuk.org/www.cancerresearchuk.org/ https://www.cancerresearchuk.org/ — 200 — 56.3 KiB — 11 ms — h2https://www.cancerresearchuk.org/_next/static/media/001e002f03b017c1-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/001e002f03b017c1-s.p.woff — 200 — 74.4 KiB — 43 ms — h2https://www.cancerresearchuk.org/_next/static/media/22f59f5d5b479322-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/22f59f5d5b479322-s.p.woff — 200 — 143.8 KiB — 54 ms — h2https://www.cancerresearchuk.org/_next/static/media/35789c96e49e6b7f-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/35789c96e49e6b7f-s.p.woff — 200 — 72.6 KiB — 44 ms — h2https://www.cancerresearchuk.org/_next/static/media/6eb962549b7dc14e-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/6eb962549b7dc14e-s.p.woff — 200 — 45.7 KiB — 42 ms — h2https://www.cancerresearchuk.org/_next/static/media/72b3d441bbdb517b-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/72b3d441bbdb517b-s.p.woff — 200 — 44.8 KiB — 43 ms — h2https://www.cancerresearchuk.org/_next/static/media/82b68f6f091d46c1-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/82b68f6f091d46c1-s.p.woff — 200 — 44.6 KiB — 43 ms — h2https://www.cancerresearchuk.org/_next/static/media/aac452a0af5508c6-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/aac452a0af5508c6-s.p.woff — 200 — 45.6 KiB — 45 ms — h2https://www.cancerresearchuk.org/_next/static/media/bb3853c711608cc5-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/bb3853c711608cc5-s.p.woff — 200 — 69.7 KiB — 49 ms — h2https://www.cancerresearchuk.org/_next/static/media/e21fa8781a9a32b3-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/e21fa8781a9a32b3-s.p.woff — 200 — 74.9 KiB — 54 ms — h2https://www.cancerresearchuk.org/_next/static/media/fb98212e27cc7064-s.p.woffwww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/media/fb98212e27cc7064-s.p.woff — 200 — 166.0 KiB — 48 ms — h2https://cdn.cookielaw.org/scripttemplates/otSDKStub.jscdn.cookielaw.org/scripttemplates/o... https://cdn.cookielaw.org/scripttemplates/otSDKStub.js — -1 — 0 B — 136 ms — https://www.cancerresearchuk.org/_next/static/css/c361d1f26b524758.csswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/css/c361d1f26b524758.css — 200 — 3.6 KiB — 16 ms — h2https://www.cancerresearchuk.org/_next/static/css/c682fa5ca7232dbe.csswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/css/c682fa5ca7232dbe.css — 200 — 3.4 KiB — 19 ms — h2https://www.cancerresearchuk.org/_next/static/css/761dc5ff23fcdfa0.csswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/css/761dc5ff23fcdfa0.css — 200 — 3.9 KiB — 17 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-KHMJ7CSwww.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-KHMJ7CS — 200 — 181.5 KiB — 161 ms — h2https://images.ctfassets.net/u7vsjnoopqo5/4uDzgmkufKEz5N4ef7374L/6418128c52a524c1ffad4a815f68ecee/cruk-logo.svgimages.ctfassets.net/u7vsjnoopqo5/4... https://images.ctfassets.net/u7vsjnoopqo5/4uDzgmkufKEz5N4ef7374L/6418128c52a524c1ffad4a815f68ecee/cruk-logo.svg — 200 — 6.7 KiB — 75 ms — h2https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F4KvYfwN2xheb6YkPFfL0Re%2F483d435617c31f7394ada12dbed5d7a8%2FDAT-DSC_0678.webp&w=1920&q=65www.cancerresearchuk.org/_next/imag... https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F4KvYfwN2xheb6YkPFfL0Re%2F483d435617c31f7394ada12dbed5d7a8%2FDAT-DSC_0678.webp&w=1920&q=65 — 200 — 66.7 KiB — 78 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/webpack-d18f008b72876714.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/webpack-d18f008b72876714.js — 200 — 5.7 KiB — 46 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/87c73c54-dd8d81ac9604067c.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/87c73c54-dd8d81ac9604067c.js — 200 — 57.6 KiB — 84 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/18-f78cdf1f90d3fe0f.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/18-f78cdf1f90d3fe0f.js — 200 — 48.2 KiB — 81 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/main-app-57aa1716f0d0f500.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/main-app-57aa1716f0d0f500.js — 200 — 3.8 KiB — 48 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/7180-be8f246206a70c65.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/7180-be8f246206a70c65.js — 200 — 174.1 KiB — 96 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/7105-e8c503187482c546.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/7105-e8c503187482c546.js — 200 — 262.6 KiB — 109 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/8619-0ff90b77525dda4d.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/8619-0ff90b77525dda4d.js — 200 — 14.5 KiB — 80 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/7852-beba7ef95a6f0242.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/7852-beba7ef95a6f0242.js — 200 — 8.3 KiB — 69 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/3295-faf68d8d3dc812dd.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/3295-faf68d8d3dc812dd.js — 200 — 6.4 KiB — 50 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/2691-38189575cf339bed.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/2691-38189575cf339bed.js — 200 — 63.7 KiB — 85 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/4925-3876f624fa71ddb4.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/4925-3876f624fa71ddb4.js — 200 — 7.3 KiB — 50 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/8520-3a0ebf73bddae698.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/8520-3a0ebf73bddae698.js — 200 — 7.4 KiB — 41 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/2563-5fb75c6b74338a9a.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/2563-5fb75c6b74338a9a.js — 200 — 3.6 KiB — 60 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/app/layout-f0fd3adaeb422483.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/app/layout-f0fd3adaeb422483.js — 200 — 5.0 KiB — 39 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/1377-c76d500bf8de9995.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/1377-c76d500bf8de9995.js — 200 — 256.0 KiB — 94 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/4052-cc3a4da56124ab29.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/4052-cc3a4da56124ab29.js — 200 — 42.6 KiB — 93 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/7693-ddc473c47d5fbf1c.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/7693-ddc473c47d5fbf1c.js — 200 — 54.9 KiB — 69 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/9978-a9b3654b2d54377b.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/9978-a9b3654b2d54377b.js — 200 — 6.6 KiB — 54 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/7186-ed9bed3cd25a7445.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/7186-ed9bed3cd25a7445.js — 200 — 55.2 KiB — 77 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/app/%5B...slug%5D/page-7bef037dcf989640.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/app/%5B...slug%5D/page-7bef037dcf989640.js — 200 — 4.5 KiB — 56 ms — h2https://www.cancerresearchuk.org/_next/static/chunks/1935.74994e1f4b1dda9b.jswww.cancerresearchuk.org/_next/stat... https://www.cancerresearchuk.org/_next/static/chunks/1935.74994e1f4b1dda9b.js — 200 — 4.2 KiB — 87 ms — h2https://www.cancerresearchuk.org/manifest.webmanifestwww.cancerresearchuk.org/manifest.w... https://www.cancerresearchuk.org/manifest.webmanifest — 200 — 3.6 KiB — 16 ms — h2https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F4F4pUV0gw1IKLdXMK9fv6x%2F7df5724f6a792f193c31d6a6f6c2587c%2FDAT-DSC_2346.webp&w=640&q=75www.cancerresearchuk.org/_next/imag... https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F4F4pUV0gw1IKLdXMK9fv6x%2F7df5724f6a792f193c31d6a6f6c2587c%2FDAT-DSC_2346.webp&w=640&q=75 — 200 — 24.4 KiB — 11 ms — h2https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F495diaqhUn1j6mGQUy39Jo%2F659246dabe28a18f7ec1a5b24d48a379%2F250406-CRUK-LdnLandMarks-LoRes063__1_.jpg&w=640&q=75www.cancerresearchuk.org/_next/imag... https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F495diaqhUn1j6mGQUy39Jo%2F659246dabe28a18f7ec1a5b24d48a379%2F250406-CRUK-LdnLandMarks-LoRes063__1_.jpg&w=640&q=75 — 200 — 44.3 KiB — 10 ms — h2https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fdownloads.ctfassets.net%2Fu7vsjnoopqo5%2F1QRy2cZ7SViCZN3FqRGg62%2F7ccd0e795041886327df0740ac0c89a8%2FLA2_6055.jpg&w=640&q=75www.cancerresearchuk.org/_next/imag... https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fdownloads.ctfassets.net%2Fu7vsjnoopqo5%2F1QRy2cZ7SViCZN3FqRGg62%2F7ccd0e795041886327df0740ac0c89a8%2FLA2_6055.jpg&w=640&q=75 — 200 — 51.0 KiB — 37 ms — h2https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F1zCaqw3t2EDgF4KYK1FmDD%2F450e5f6b14fa378e18f33208aa997dea%2FDAT-GettyImages-622271296.webp&w=640&q=75www.cancerresearchuk.org/_next/imag... https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F1zCaqw3t2EDgF4KYK1FmDD%2F450e5f6b14fa378e18f33208aa997dea%2FDAT-GettyImages-622271296.webp&w=640&q=75 — 200 — 26.1 KiB — 38 ms — h2https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F7pvuXtMi9viFVzvAA7amNl%2F24d9b01257ad7eb9e400945308a110ad%2FDAT-CRUK1__2___1_.webp&w=640&q=75www.cancerresearchuk.org/_next/imag... https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F7pvuXtMi9viFVzvAA7amNl%2F24d9b01257ad7eb9e400945308a110ad%2FDAT-CRUK1__2___1_.webp&w=640&q=75 — 200 — 20.4 KiB — 39 ms — h2https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F4wNwoKuihmXzphYWDIJAZN%2F5406c34c2d6f01e53cb7ad11c200a2fc%2FBreakthroughs_that_matter_-_Card.png&w=640&q=75www.cancerresearchuk.org/_next/imag... https://www.cancerresearchuk.org/_next/image?url=https%3A%2F%2Fimages.ctfassets.net%2Fu7vsjnoopqo5%2F4wNwoKuihmXzphYWDIJAZN%2F5406c34c2d6f01e53cb7ad11c200a2fc%2FBreakthroughs_that_matter_-_Card.png&w=640&q=75 — 200 — 9.8 KiB — 36 ms — h2https://www.cancerresearchuk.org/favicon.icowww.cancerresearchuk.org/favicon.ic... https://www.cancerresearchuk.org/favicon.ico — 200 — 29.1 KiB — 5 ms — h2https://www.cancerresearchuk.org/icons/cruk-logo.svgwww.cancerresearchuk.org/icons/cruk... https://www.cancerresearchuk.org/icons/cruk-logo.svg — 200 — 9.2 KiB — 4 ms — h2https://www.googletagmanager.com/gtag/js?id=G-58736Z2GNN&cx=c&gtm=4e64h1www.googletagmanager.com/gtag/js?id... https://www.googletagmanager.com/gtag/js?id=G-58736Z2GNN&cx=c&gtm=4e64h1 — 200 — 168.3 KiB — 43 ms — h2https://www.googletagmanager.com/gtag/js?id=AW-986083629&cx=c&gtm=4e64h1www.googletagmanager.com/gtag/js?id... https://www.googletagmanager.com/gtag/js?id=AW-986083629&cx=c&gtm=4e64h1 — 200 — 137.3 KiB — 70 ms — h2https://www.googletagmanager.com/gtag/js?id=DC-8727222&cx=c&gtm=4e64h1www.googletagmanager.com/gtag/js?id... https://www.googletagmanager.com/gtag/js?id=DC-8727222&cx=c&gtm=4e64h1 — 200 — 130.1 KiB — 58 ms — h2https://chat.system.gnatta.com/script/app.jschat.system.gnatta.com/script/app.j... https://chat.system.gnatta.com/script/app.js — 200 — 21.8 KiB — 149 ms — h2https://pagead2.googlesyndication.com/ccm/collect?rcb=10&frm=0&en=page_view&dl=https%3A%2F%2Fwww.cancerresearchuk.org%2F&scrsrc=www.googletagmanager.com&rnd=790301804.1776812167&navt=n&npa=1&_tu=CA&gtm=45fe64h1v9181629518z89134183385za20gzb9134183385zd9134183385xec&gcs=G100&gcd=13p3pPp2p5l1&dma_cps=-&dma=1&tag_exp=0~115938465~115938469~117266400&apve=1&apvf=f&apvc=1&tids=DC-8727222&tid=DC-8727222&tft=1776812167140&tfd=1129pagead2.googlesyndication.com/ccm/c... https://pagead2.googlesyndication.com/ccm/collect?rcb=10&frm=0&en=page_view&dl=https%3A%2F%2Fwww.cancerresearchuk.org%2F&scrsrc=www.googletagmanager.com&rnd=790301804.1776812167&navt=n&npa=1&_tu=CA&gtm=45fe64h1v9181629518z89134183385za20gzb9134183385zd9134183385xec&gcs=G100&gcd=13p3pPp2p5l1&dma_cps=-&dma=1&tag_exp=0~115938465~115938469~117266400&apve=1&apvf=f&apvc=1&tids=DC-8727222&tid=DC-8727222&tft=1776812167140&tfd=1129 — 200 — 21 B — 76 ms — h3https://pagead2.googlesyndication.com/ccm/collect?rcb=12&frm=0&en=page_view&dl=https%3A%2F%2Fwww.cancerresearchuk.org%2F&scrsrc=www.googletagmanager.com&rnd=790301804.1776812167&navt=n&npa=1&_tu=CA&gtm=45be64h1v9181461255z89134183385za20gzb9134183385zd9134183385xec&gcs=G100&gcd=13p3pPp2p5l1&dma_cps=-&dma=1&tag_exp=0~115938465~115938468~117266401&apve=1&apvf=f&apvc=0&tids=AW-986083629&tid=AW-986083629&tft=1776812167149&tfd=1138pagead2.googlesyndication.com/ccm/c... https://pagead2.googlesyndication.com/ccm/collect?rcb=12&frm=0&en=page_view&dl=https%3A%2F%2Fwww.cancerresearchuk.org%2F&scrsrc=www.googletagmanager.com&rnd=790301804.1776812167&navt=n&npa=1&_tu=CA&gtm=45be64h1v9181461255z89134183385za20gzb9134183385zd9134183385xec&gcs=G100&gcd=13p3pPp2p5l1&dma_cps=-&dma=1&tag_exp=0~115938465~115938468~117266401&apve=1&apvf=f&apvc=0&tids=AW-986083629&tid=AW-986083629&tft=1776812167149&tfd=1138 — 200 — 21 B — 73 ms — h3
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 652ms · 942KB · €10/mo
www.cancerresearchuk.org
Other
Optional
Execution 168ms
Transfer 48 KB
Monthly Cost €3/mo
www.cancerresearchuk.org
Other
Optional
Execution 113ms
Transfer 56 KB
Monthly Cost €2/mo
www.cancerresearchuk.org
Other
Optional
Execution 102ms
Transfer 263 KB
Unused 18%
Monthly Cost €2/mo
Unattributable
Other
Optional
Execution 84ms
Transfer 0 KB
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 66ms
Transfer 181 KB
Unused 43%
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 64ms
Transfer 137 KB
Unused 48%
Monthly Cost €1/mo
www.cancerresearchuk.org
Other
Optional
Execution 57ms
Transfer 256 KB
Unused 16%
Monthly Cost €1/mo

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

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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