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.
9.57 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
27.67 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
1.84 s
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.
9.66 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.
28.08 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 sFPage Weight BudgetAction5.3 MB transferred, 88 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
FJS Execution CostAction8140ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://nrl.iucnredlist.org/packs/redlist-91968a82c64c481f2989.js | 2187ms | 1433ms | 721ms | 3rd |
| https://www.iucnredlist.org/ | 1292ms | 58ms | 4ms | 3rd |
| Unattributable | 1284ms | 120ms | 0ms | 3rd |
| https://www.iucnredlist.org/cdn-cgi/challenge-platform/scripts/jsd/main.js | 925ms | 881ms | 18ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-6HJED7KZLB&cx=c>m=4e64h1 | 360ms | 283ms | 74ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-T3K17G40FC&cx=c>m=4e64h1 | 336ms | 268ms | 65ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=UA-11409245-5&cx=c>m=4e64h1 | 331ms | 230ms | 60ms | 3rd |
| https://www.iucnredlist.org/cdn-cgi/scripts/7d0fa10a/cloudflare-static/rocket-loader.min.js | 316ms | 184ms | 6ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=UA-11409245-6&cx=c>m=4e64h1 | 258ms | 194ms | 58ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-66YGJWTDLZ&cx=c>m=4e64h1 | 252ms | 187ms | 62ms | 3rd |
Showing top 10 of 14 scripts
FJS BundlesAction13 scripts, 1.0 MB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://nrl.iucnredlist.org/packs/redlist-91968a82c64c481f2989.js | 1445 KB | 638 KB (46%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=UA-11409245-6&cx=c>m=4e64h1 | 125 KB | 65 KB (52%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=UA-11409245-5&cx=c>m=4e64h1 | 125 KB | 65 KB (52%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-T3K17G40FC&cx=c>m=4e64h1 | 146 KB | 65 KB (45%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-6HJED7KZLB&cx=c>m=4e64h1 | 146 KB | 65 KB (45%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=UA-11409245-4 | 125 KB | 63 KB (51%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-66YGJWTDLZ&cx=c>m=4e64h1 | 146 KB | 63 KB (43%) | ✓ | 3rd |
| https://nrl.iucnredlist.org/assets/application-38c0ffd83a61759780bd4ed4d32e23b4c07893f0974378780be39259de4ad5ac.js | 138 KB | 24 KB (17%) | ✓ | 3rd |
| https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da1771523124516 | 11 KB | — | ✓ | 3rd |
| https://www.iucnredlist.org/cdn-cgi/challenge-platform/h/b/scripts/jsd/0b8fb825cb67/main.js? | 11 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 InventoryAction88 resources · 5.3 MB · 1.0 MB savings availableFIX
~1.0 MiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 88 resources | 5.3 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction55 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
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
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
A+Text CompressionAll text resources are compressedPASS
A+Font Loading6 fonts (342 KB)PASS
Web fonts
6
342 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
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 Waterfall88 requests over 2056msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
nrl.iucnredlist.org nrl.iucnredlist.org | Other | 2187ms | 1445 KB | 46% | $29/mo | Costly |
www.iucnredlist.org www.iucnredlist.org | Other | 1292ms | 12 KB | — | $17/mo | Costly |
Unattributable Unattributable | Other | 1284ms | 0 KB | — | $17/mo | Costly |
www.iucnredlist.org www.iucnredlist.org | Other | 925ms | 0 KB | — | $12/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 360ms | 146 KB | 45% | $5/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 336ms | 146 KB | 45% | $4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 331ms | 125 KB | 52% | $4/mo | Costly |
www.iucnredlist.org www.iucnredlist.org | Other | 316ms | 4 KB | — | $4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 258ms | 125 KB | 52% | $3/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 252ms | 146 KB | 43% | $3/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 242ms | 125 KB | 51% | $3/mo | Costly |
nrl.iucnredlist.org nrl.iucnredlist.org | Other | 166ms | 138 KB | 17% | $2/mo | Optional |
Google Analytics www.google-analytics.com | Analytics | 114ms | 21 KB | — | $2/mo | Optional |
static.cloudflareinsights.com static.cloudflareinsights.com | Other | 76ms | 11 KB | — | $1/mo | Optional |
These scripts may cost more than they're worth
- nrl.iucnredlist.org adds 2187ms and costs ~$29/month
- www.iucnredlist.org adds 1292ms and costs ~$17/month
- Unattributable adds 1284ms and costs ~$17/month
- www.iucnredlist.org adds 925ms and costs ~$12/month
- Google Tag Manager adds 360ms and costs ~$5/month
- Google Tag Manager adds 336ms and costs ~$4/month
- Google Tag Manager adds 331ms and costs ~$4/month
- www.iucnredlist.org adds 316ms and costs ~$4/month
- Google Tag Manager adds 258ms and costs ~$3/month
- Google Tag Manager adds 252ms and costs ~$3/month
- Google Tag Manager adds 242ms 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
nrl.iucnredlist.org takes 2187ms 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.iucnredlist.org takes 1292ms 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 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.iucnredlist.org takes 925ms 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 360ms 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 336ms 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 331ms 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 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
www.iucnredlist.org takes 316ms 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
52% 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
Google Tag Manager takes 252ms 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 242ms 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
51% 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