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.
3.83 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
5.41 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
2.43 s
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.210
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
4.82 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.
19.53 s
Page Load Progression
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
FJS Execution CostAction7610ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| Unattributable | 1713ms | 126ms | 0ms | 3rd |
| https://www.futurelearn.com/ | 1284ms | 65ms | 1ms | 3rd |
| https://www.futurelearn.com/_next/static/chunks/pages/_app-635314d0893c6f83.js | 699ms | 443ms | 139ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-TDF2LGF&l=gtmDataLayer | 614ms | 510ms | 81ms | 3rd |
| https://www.futurelearn.com/_next/static/chunks/framework-b0ec748c7a4c483a.js | 543ms | 506ms | 18ms | 3rd |
| https://www.futurelearn.com/cdn-cgi/challenge-platform/scripts/jsd/main.js | 450ms | 405ms | 3ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-JW7YPD9WBP&l=gtmDataLayer&cx=c>m=4e64h1h1 | 435ms | 357ms | 64ms | 3rd |
| https://connect.facebook.net/signals/config/783518442847773?v=2.9.303&r=stable&domain=www.futurelearn.com&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 | 349ms | 295ms | 53ms | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-973080445&l=gtmDataLayer&cx=c>m=4e64h1h1 | 299ms | 239ms | 56ms | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=DC-9853912&l=gtmDataLayer&cx=c>m=4e64h1h1 | 258ms | 212ms | 42ms | 3rd |
Showing top 10 of 18 scripts
FJS BundlesAction40 scripts, 519 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.futurelearn.com/_next/static/chunks/pages/_app-635314d0893c6f83.js | 286 KB | 197 KB (69%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-JW7YPD9WBP&l=gtmDataLayer&cx=c>m=4e64h1h1 | 178 KB | 69 KB (39%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=DC-9853912&l=gtmDataLayer&cx=c>m=4e64h1h1 | 129 KB | 63 KB (48%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-TDF2LGF&l=gtmDataLayer | 184 KB | 62 KB (34%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-973080445&l=gtmDataLayer&cx=c>m=4e64h1h1 | 144 KB | 61 KB (43%) | ✓ | 3rd |
| https://connect.facebook.net/signals/config/783518442847773?v=2.9.303&r=stable&domain=www.futurelearn.com&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 | 125 KB | 35 KB (28%) | ✓ | 3rd |
| https://connect.facebook.net/en_US/fbevents.js | 97 KB | 34 KB (35%) | ✓ | 3rd |
| https://www.futurelearn.com/frontend/utils/optanonWrapper.js | 1 KB | — | ✓ | 3rd |
| https://secure.quantserve.com/quant.js | 12 KB | — | ✓ | 3rd |
| https://www.futurelearn.com/_next/static/chunks/4284-9994afde6d936cb1.js | 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
FPage Weight InventoryAction127 resources · 2.0 MB · 519 KB savings availableFIX
~519.1 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 127 resources | 2.0 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CPage Weight BudgetAction2.0 MB transferred, 127 requestsREVIEW
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
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.
Source: web.dev
BImage Optimization35 images, 0 KB saveableREVIEW
A+Text CompressionAll text resources are compressedPASS
A+Font Loading4 fonts (74 KB)PASS
Web fonts
4
74 KB total
Render-blocking
0
of 4
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
A+Green HostingWhether the site is served from green-energy infrastructurePASS
Green Hosting
This site is hosted on green energy infrastructure
Provider: Cloudflare
Network Waterfall127 requests over 12248msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
Unattributable Unattributable | Other | 1713ms | 0 KB | — | $23/mo | Costly |
www.futurelearn.com www.futurelearn.com | Other | 1284ms | 128 KB | — | $17/mo | Costly |
www.futurelearn.com www.futurelearn.com | Other | 699ms | 286 KB | 69% | $9/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 614ms | 184 KB | 34% | $8/mo | Costly |
www.futurelearn.com www.futurelearn.com | Other | 543ms | 44 KB | — | $7/mo | Costly |
www.futurelearn.com www.futurelearn.com | Other | 450ms | 0 KB | — | $6/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 435ms | 178 KB | 39% | $6/mo | Costly |
Facebook Pixel connect.facebook.net | Advertising | 349ms | 125 KB | 28% | $5/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 299ms | 144 KB | 43% | $4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 258ms | 129 KB | 48% | $3/mo | Costly |
Microsoft Clarity scripts.clarity.ms | Session Replay | 231ms | 26 KB | — | $3/mo | Costly |
tags.srv.stackadapt.com tags.srv.stackadapt.com | Other | 168ms | 8 KB | — | $2/mo | Optional |
Facebook Pixel connect.facebook.net | Advertising | 161ms | 97 KB | 35% | $2/mo | Optional |
Google Analytics www.google-analytics.com | Analytics | 95ms | 21 KB | — | $1/mo | Optional |
www.futurelearn.com www.futurelearn.com | Other | 92ms | 1 KB | — | $1/mo | Optional |
LinkedIn Insight snap.licdn.com | Advertising | 86ms | 19 KB | — | $1/mo | Optional |
www.futurelearn.com www.futurelearn.com | Other | 74ms | 36 KB | — | $1/mo | Optional |
www.futurelearn.com www.futurelearn.com | Other | 57ms | 0 KB | — | $1/mo | Optional |
These scripts may cost more than they're worth
- Unattributable adds 1713ms and costs ~$23/month
- www.futurelearn.com adds 1284ms and costs ~$17/month
- www.futurelearn.com adds 699ms and costs ~$9/month
- Google Tag Manager adds 614ms and costs ~$8/month
- www.futurelearn.com adds 543ms and costs ~$7/month
- www.futurelearn.com adds 450ms and costs ~$6/month
- Google Tag Manager adds 435ms and costs ~$6/month
- Facebook Pixel adds 349ms and costs ~$5/month
- Google Tag Manager adds 299ms and costs ~$4/month
- Google Tag Manager adds 258ms and costs ~$3/month
- Microsoft Clarity adds 231ms 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
Unattributable takes 1713ms 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.futurelearn.com takes 1284ms 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.futurelearn.com takes 699ms 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
69% of www.futurelearn.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
Google Tag Manager takes 614ms 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.futurelearn.com takes 543ms 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.futurelearn.com takes 450ms 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 435ms 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
Facebook Pixel takes 349ms 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 299ms 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 258ms 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
Microsoft Clarity takes 231ms 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