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.
5.33 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
16.09 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
876 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.027
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
5.39 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.
16.30 s
Page Load Progression
FPage Weight BudgetAction2.7 MB transferred, 90 requestsFIX
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
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
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 CostAction2988ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtm.js?id=GTM-KQZ3W5 | 421ms | 349ms | 60ms | 3rd |
| Unattributable | 406ms | 95ms | 0ms | 3rd |
| https://www.redditstatic.com/ads/pixel.js | 383ms | 343ms | 5ms | 3rd |
| https://app.termly.io/resource-blocker/83c28410-26f6-4523-a7d3-466c377cb83f?autoBlock=off | 308ms | 247ms | 48ms | 3rd |
| https://www.qmul.ac.uk/ | 269ms | 14ms | 3ms | 3rd |
| https://analytics.tiktok.com/i18n/pixel/static/main.MWE0ZWQ3ZWQwOA.js | 255ms | 207ms | 45ms | 3rd |
| https://connect.facebook.net/signals/config/1148425983053697?v=2.9.303&r=stable&domain=www.qmul.ac.uk&hme=97937018cefade17726f0472876fc101316b2ce9008a35a6a5a7977d7436151a&ex_m=104%2C205%2C154%2C22%2C72%2C73%2C145%2C68%2C67%2C11%2C162%2C90%2C16%2C138%2C127%2C39%2C75%2C78%2C134%2C159%2C164%2C8%2C4%2C5%2C7%2C6%2C3%2C91%2C101%2C165%2C170%2C219%2C62%2C186%2C187%2C55%2C276%2C30%2C74%2C231%2C230%2C229%2C23%2C33%2C103%2C61%2C10%2C63%2C97%2C98%2C99%2C105%2C130%2C31%2C29%2C132%2C133%2C129%2C128%2C155%2C76%2C158%2C156%2C157%2C50%2C60%2C123%2C15%2C161%2C45%2C263%2C264%2C262%2C26%2C27%2C28%2C48%2C146%2C77%2C112%2C18%2C20%2C44%2C40%2C42%2C41%2C83%2C92%2C96%2C110%2C144%2C147%2C46%2C111%2C24%2C21%2C119%2C69%2C36%2C149%2C148%2C150%2C141%2C139%2C25%2C35%2C59%2C109%2C160%2C70%2C17%2C152%2C114%2C81%2C66%2C19%2C85%2C86%2C116%2C84%2C136%2C135%2C34%2C278%2C293%2C212%2C201%2C202%2C200%2C296%2C288%2C52%2C213%2C107%2C131%2C80%2C121%2C54%2C47%2C49%2C113%2C120%2C126%2C58%2C64%2C151%2C115%2C37%2C32%2C53%2C56%2C100%2C163%2C1%2C124%2C14%2C122%2C12%2C2%2C57%2C93%2C65%2C118%2C89%2C88%2C166%2C167%2C94%2C95%2C9%2C125%2C102%2C51%2C142%2C87%2C79%2C71%2C117%2C106%2C43%2C143%2C0%2C82%2C137%2C140%2C153%2C38%2C108%2C13%2C168 | 214ms | 184ms | 29ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-16588318700&cx=c>m=4e64h1 | 127ms | 96ms | 30ms | 3rd |
| https://connect.facebook.net/en_US/fbevents.js | 117ms | 82ms | 34ms | 3rd |
| https://sc-static.net/scevent.min.js | 101ms | 90ms | 5ms | 3rd |
Showing top 10 of 16 scripts
DJS BundlesAction33 scripts, 459 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://analytics.tiktok.com/i18n/pixel/static/main.MWE0ZWQ3ZWQwMQ.js | 110 KB | 85 KB (77%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-16588318700&cx=c>m=4e64h1 | 145 KB | 81 KB (56%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-KQZ3W5 | 197 KB | 67 KB (34%) | ✓ | 3rd |
| https://analytics.tiktok.com/i18n/pixel/static/main.MWE0ZWQ3ZWQwOA.js | 117 KB | 61 KB (52%) | ✓ | 3rd |
| https://app.termly.io/resource-blocker/83c28410-26f6-4523-a7d3-466c377cb83f?autoBlock=off | 143 KB | 54 KB (38%) | ✓ | 3rd |
| https://www.qmul.ac.uk/media/ow-assets/assets/js/vendors~lib.min.1.2.4.js | 53 KB | 43 KB (82%) | ✓ | 3rd |
| https://connect.facebook.net/signals/config/1148425983053697?v=2.9.303&r=stable&domain=www.qmul.ac.uk&hme=97937018cefade17726f0472876fc101316b2ce9008a35a6a5a7977d7436151a&ex_m=104%2C205%2C154%2C22%2C72%2C73%2C145%2C68%2C67%2C11%2C162%2C90%2C16%2C138%2C127%2C39%2C75%2C78%2C134%2C159%2C164%2C8%2C4%2C5%2C7%2C6%2C3%2C91%2C101%2C165%2C170%2C219%2C62%2C186%2C187%2C55%2C276%2C30%2C74%2C231%2C230%2C229%2C23%2C33%2C103%2C61%2C10%2C63%2C97%2C98%2C99%2C105%2C130%2C31%2C29%2C132%2C133%2C129%2C128%2C155%2C76%2C158%2C156%2C157%2C50%2C60%2C123%2C15%2C161%2C45%2C263%2C264%2C262%2C26%2C27%2C28%2C48%2C146%2C77%2C112%2C18%2C20%2C44%2C40%2C42%2C41%2C83%2C92%2C96%2C110%2C144%2C147%2C46%2C111%2C24%2C21%2C119%2C69%2C36%2C149%2C148%2C150%2C141%2C139%2C25%2C35%2C59%2C109%2C160%2C70%2C17%2C152%2C114%2C81%2C66%2C19%2C85%2C86%2C116%2C84%2C136%2C135%2C34%2C278%2C293%2C212%2C201%2C202%2C200%2C296%2C288%2C52%2C213%2C107%2C131%2C80%2C121%2C54%2C47%2C49%2C113%2C120%2C126%2C58%2C64%2C151%2C115%2C37%2C32%2C53%2C56%2C100%2C163%2C1%2C124%2C14%2C122%2C12%2C2%2C57%2C93%2C65%2C118%2C89%2C88%2C166%2C167%2C94%2C95%2C9%2C125%2C102%2C51%2C142%2C87%2C79%2C71%2C117%2C106%2C43%2C143%2C0%2C82%2C137%2C140%2C153%2C38%2C108%2C13%2C168 | 127 KB | 36 KB (29%) | ✓ | 3rd |
| https://connect.facebook.net/en_US/fbevents.js | 99 KB | 33 KB (34%) | ✓ | 3rd |
| https://bat.bing.com/p/action/85083482.js | 1 KB | — | ✓ | 3rd |
| https://bat.bing.com/p/conversions/t/85083482?insights=1 | 1 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 InventoryAction90 resources · 2.7 MB · 459 KB savings availableFIX
~458.8 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 90 resources | 2.7 MiB | ||||||
CImage OptimizationAction18 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
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 Loading3 fonts (210 KB)PASS
Web fonts
3
210 KB total
Render-blocking
0
of 3
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
AHTTP Cachingmax-age=86400 (1 day)PASS
max-age=86400
| Directive | Value | Meaning |
|---|---|---|
| max-age | 86400 | Cache for 1 day |
Network Waterfall90 requests over 1654msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
Google Tag Manager www.googletagmanager.com | Tag Manager | 421ms | 197 KB | 34% | £4/mo | Costly |
Unattributable Unattributable | Other | 406ms | 0 KB | — | £4/mo | Costly |
www.redditstatic.com www.redditstatic.com | Other | 383ms | 19 KB | — | £4/mo | Costly |
app.termly.io app.termly.io | Other | 308ms | 143 KB | 38% | £3/mo | Costly |
www.qmul.ac.uk www.qmul.ac.uk | Other | 269ms | 15 KB | — | £3/mo | Costly |
analytics.tiktok.com analytics.tiktok.com | Other | 255ms | 117 KB | 52% | £3/mo | Costly |
Facebook Pixel connect.facebook.net | Advertising | 214ms | 127 KB | 29% | £2/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 127ms | 145 KB | 56% | £1/mo | Optional |
Facebook Pixel connect.facebook.net | Advertising | 117ms | 99 KB | 34% | £1/mo | Optional |
sc-static.net sc-static.net | Other | 101ms | 25 KB | — | £1/mo | Optional |
analytics.tiktok.com analytics.tiktok.com | Other | 100ms | 110 KB | 77% | £1/mo | Optional |
www.qmul.ac.uk www.qmul.ac.uk | Other | 66ms | 31 KB | — | £1/mo | Optional |
Facebook Pixel connect.facebook.net | Advertising | 60ms | 17 KB | — | £1/mo | Optional |
Bing UET bat.bing.com | Advertising | 57ms | 16 KB | — | £1/mo | Optional |
Facebook Pixel connect.facebook.net | Advertising | 53ms | 19 KB | — | £1/mo | Optional |
LinkedIn Insight snap.licdn.com | Advertising | 51ms | 19 KB | — | £1/mo | Optional |
These scripts may cost more than they're worth
- Google Tag Manager adds 421ms and costs ~£4/month
- Unattributable adds 406ms and costs ~£4/month
- www.redditstatic.com adds 383ms and costs ~£4/month
- app.termly.io adds 308ms and costs ~£3/month
- www.qmul.ac.uk adds 269ms and costs ~£3/month
- analytics.tiktok.com adds 255ms and costs ~£3/month
- Facebook Pixel adds 214ms 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
Google Tag Manager takes 421ms 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 406ms 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
www.redditstatic.com takes 383ms 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
app.termly.io takes 308ms 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
www.qmul.ac.uk takes 269ms 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
analytics.tiktok.com takes 255ms 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
52% of analytics.tiktok.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
Facebook Pixel takes 214ms 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
56% of Google Tag Manager'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
77% of analytics.tiktok.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