Performance
· 17 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.
5.78 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
15.36 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
296 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.078
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
5.78 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.
15.53 s
Page Load Progression
FPage Weight BudgetAction9.0 MB transferred, 77 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 Execution CostAction2112ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.citystgeorges.ac.uk/ | 682ms | 13ms | 1ms | 3rd |
| Unattributable | 453ms | 7ms | 0ms | 3rd |
| https://consent.cookiebot.com/uc.js?cbid=d20f0709-234f-4c30-b3b6-1298df75d244&implementation=gtm&consentmode-dataredaction=dynamic | 427ms | 222ms | 8ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-5B77FVX | 330ms | 276ms | 49ms | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/main.js?v=2026.04.14 | 143ms | 76ms | 9ms | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/search.js?v=2026.04.14 | 77ms | 67ms | 6ms | 3rd |
DPage Weight InventoryAction77 resources · 9.0 MB · 196 KB savings availableFIX
~195.9 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 77 resources | 9.0 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction36 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
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
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
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 BundlesAction11 scripts, 196 KB unusedREVIEW
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtm.js?id=GTM-5B77FVX | 194 KB | 84 KB (43%) | ✓ | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/vendor-direct.js?v=2026.04.14 | 36 KB | 36 KB (99%) | ✓ | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/vendor-dependencies.js?v=2026.04.14 | 35 KB | 29 KB (82%) | ✓ | 3rd |
| https://consent.cookiebot.com/d20f0709-234f-4c30-b3b6-1298df75d244/cc.js?renew=false&referer=www.citystgeorges.ac.uk&dnt=false&init=false | 112 KB | 25 KB (23%) | ✓ | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/main.js?v=2026.04.14 | 27 KB | 22 KB (81%) | ✓ | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/core.js?v=2026.04.14 | 26 KB | — | ✓ | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/axios.js?v=2026.04.14 | 7 KB | — | ✓ | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/react.js?v=2026.04.14 | 39 KB | — | ✓ | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/search.js?v=2026.04.14 | 16 KB | — | ✓ | 3rd |
| https://www.citystgeorges.ac.uk/__data/assets/git_bridge/0011/976169/main/js/browser-search-box.js?v=2026.04.14 | 6 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
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 Loading14 fonts (315 KB)PASS
Web fonts
14
315 KB total
Render-blocking
0
of 14
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
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
A+Third-Party ResourcesNo third-party resources detectedPASS
Network Waterfall77 requests over 862msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.citystgeorges.ac.uk www.citystgeorges.ac.uk | Other | 682ms | 35 KB | — | £7/mo | Costly |
Unattributable Unattributable | Other | 453ms | 0 KB | — | £5/mo | Costly |
consent.cookiebot.com consent.cookiebot.com | Other | 427ms | 27 KB | — | £4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 330ms | 194 KB | 43% | £3/mo | Costly |
www.citystgeorges.ac.uk www.citystgeorges.ac.uk | Other | 143ms | 27 KB | 81% | £1/mo | Optional |
www.citystgeorges.ac.uk www.citystgeorges.ac.uk | Other | 77ms | 16 KB | — | £1/mo | Optional |
These scripts may cost more than they're worth
- www.citystgeorges.ac.uk adds 682ms and costs ~£7/month
- Unattributable adds 453ms and costs ~£5/month
- consent.cookiebot.com adds 427ms and costs ~£4/month
- Google Tag Manager adds 330ms and costs ~£3/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
www.citystgeorges.ac.uk takes 682ms 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
Unattributable takes 453ms 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
consent.cookiebot.com takes 427ms 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
Google Tag Manager takes 330ms 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
81% of www.citystgeorges.ac.uk'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