Performance
· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.Performance-focused optimization plan with CWV assessment, top offenders, and time estimates
First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.
1.11 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
2.32 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
98 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.
1.46 s
Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.
4.23 s
Page Load Progression
FPage Weight BudgetAction4.7 MB transferred, 69 requestsFIX
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.
Source: web.dev
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
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.
Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).
Source: web.dev font loading
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
DJS BundlesAction28 scripts, 430 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://metrics.ncl.ac.uk/gtag/js?id=G-VH2F6S16XP&cx=c>m=4e64k0h2&sign=c8466af07364d8b6218eaaa1b5593b460bdaeca08b236b87de8f094c1f781d62_20260421 | 205 KB | 78 KB (38%) | ✓ | 3rd |
| https://metrics.ncl.ac.uk/gtag/js?id=AW-777937483&cx=c>m=4e64k0h2&sign=c8466af07364d8b6218eaaa1b5593b460bdaeca08b236b87de8f094c1f781d62_20260421 | 166 KB | 73 KB (44%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-380968450&cx=c>m=4e64k0h2&sign=c8466af07364d8b6218eaaa1b5593b460bdaeca08b236b87de8f094c1f781d62_20260421 | 144 KB | 65 KB (45%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=DC-12430850&cx=c>m=4e64k0h2&sign=c8466af07364d8b6218eaaa1b5593b460bdaeca08b236b87de8f094c1f781d62_20260421 | 130 KB | 63 KB (48%) | ✓ | 3rd |
| https://metrics.ncl.ac.uk/gtm.js?id=GTM-5HH99Z | 229 KB | 62 KB (27%) | ✓ | 3rd |
| https://script.hotjar.com/modules.6a0f3932cb1341a35c18.js | 57 KB | 36 KB (65%) | ✓ | 3rd |
| https://consent.cookiebot.com/1ebf835b-c525-4423-9bd4-669b6cf0b7cd/cc.js?renew=false&referer=www.ncl.ac.uk&dnt=false&init=false | 172 KB | 31 KB (18%) | ✓ | 3rd |
| https://consent.cookiebot.com/uc.js | 36 KB | 23 KB (64%) | ✓ | 3rd |
| https://www.youtube.com/iframe_api?apiKey=AIzaSyAAH_WLyeIGyalKrINKwCCXzIWhQDbno_g | 4 KB | — | ✓ | 3rd |
| https://www.ncl.ac.uk/webtemplate/js/dist/lib/ncuvision__slick.min.js | 12 KB | — | ✓ | 3rd |
Consider code splitting or tree shaking to reduce unused code.
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.
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.
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.
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.
This bundle has high unused code — code-split or tree-shake to ship only what executes.
Source: web.dev / Lighthouse coverage
FPage Weight InventoryAction69 resources · 4.7 MB · 430 KB savings availableFIX
~430.2 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 69 resources | 4.7 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction19 images, 0 KB saveableREVIEW
Set explicit width and height to prevent CLS.
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.
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.
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.
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.
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.
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
CJS Execution CostAction1064ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://consent.cookiebot.com/uc.js | 219ms | 105ms | 2ms | 3rd |
| https://code.jquery.com/jquery-3.7.1.min.js | 184ms | 93ms | 2ms | 3rd |
| Unattributable | 135ms | 3ms | 0ms | 3rd |
| https://www.ncl.ac.uk/ | 135ms | 3ms | 1ms | 3rd |
| https://metrics.ncl.ac.uk/gtm.js?id=GTM-5HH99Z | 131ms | 108ms | 15ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=DC-12430850&cx=c>m=4e64k0h2&sign=c8466af07364d8b6218eaaa1b5593b460bdaeca08b236b87de8f094c1f781d62_20260421 | 100ms | 91ms | 8ms | 3rd |
| https://scripts.clarity.ms/0.8.60-beta/clarity.js | 97ms | 84ms | 2ms | 3rd |
| https://metrics.ncl.ac.uk/gtag/js?id=G-VH2F6S16XP&cx=c>m=4e64k0h2&sign=c8466af07364d8b6218eaaa1b5593b460bdaeca08b236b87de8f094c1f781d62_20260421 | 62ms | 52ms | 10ms | 3rd |
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
No green hosting detected
A+Text CompressionAll text resources are compressedPASS
A+Font Loading6 fonts (221 KB)PASS
Web fonts
6
221 KB total
Render-blocking
0
of 6
Dominant font-display
swap
Most common across fonts
Font loading timeline
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 CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
Network Waterfall69 requests over 4248msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
consent.cookiebot.com consent.cookiebot.com | Other | 219ms | 36 KB | 64% | £2/mo | Costly |
code.jquery.com code.jquery.com | Other | 184ms | 30 KB | — | £2/mo | Optional |
Unattributable Unattributable | Other | 135ms | 0 KB | — | £1/mo | Optional |
www.ncl.ac.uk www.ncl.ac.uk | Other | 135ms | 24 KB | — | £1/mo | Optional |
metrics.ncl.ac.uk metrics.ncl.ac.uk | Other | 131ms | 229 KB | 27% | £1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 100ms | 130 KB | 48% | £1/mo | Optional |
Microsoft Clarity scripts.clarity.ms | Session Replay | 97ms | 25 KB | — | £1/mo | Optional |
metrics.ncl.ac.uk metrics.ncl.ac.uk | Other | 62ms | 205 KB | 38% | £1/mo | Optional |
These scripts may cost more than they're worth
- consent.cookiebot.com adds 219ms and costs ~£2/month
100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.
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
consent.cookiebot.com takes 219ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
64% of consent.cookiebot.com's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev