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.
761 ms
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
1.37 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
22 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.254
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
1.24 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.
3.24 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 BudgetAction3.1 MB transferred, 68 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
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
FJS BundlesAction24 scripts, 672 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://cdn.taboola.com/libtrc/sciencealert/loader.js | 326 KB | 209 KB (64%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-VT6ZH45353&cx=c>m=4e64h1 | 178 KB | 114 KB (64%) | ✓ | 3rd |
| https://bordeaux.futurecdn.net/bordeaux.js | 159 KB | 90 KB (57%) | ✓ | 3rd |
| https://www.google.com/cse/static/element/dc329f57de078f5d/cse_element__en.js?usqp=CAM%3D | 103 KB | 70 KB (68%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-VT6ZH45353 | 178 KB | 68 KB (38%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-T9C3TSJQ | 120 KB | 62 KB (52%) | ✓ | 3rd |
| https://6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app/6093eccf-6734-4877-ac8b-83d6d0e27b46-web.js | 256 KB | 38 KB (15%) | ✓ | 3rd |
| https://www.sciencealert.com/wp-includes/js/jquery/jquery.min.js?ver=3.7.1 | 30 KB | 21 KB (72%) | ✓ | 3rd |
| https://www.sciencealert.com/wp-includes/js/jquery/jquery-migrate.min.js?ver=3.4.1 | 5 KB | — | ✓ | 3rd |
| https://scripts.clarity.ms/0.8.59/clarity.js | 26 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 InventoryAction68 resources · 3.1 MB · 672 KB savings availableFIX
~671.8 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 68 resources | 3.1 MiB | ||||||
BImage Optimization20 images, 0 KB saveableREVIEW
BJS Execution Cost541ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.sciencealert.com/ | 113ms | 33ms | 3ms | 3rd |
| Unattributable | 95ms | 18ms | 0ms | 3rd |
| https://cdn.taboola.com/libtrc/sciencealert/loader.js | 88ms | 52ms | 36ms | 3rd |
| https://6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app/6093eccf-6734-4877-ac8b-83d6d0e27b46-web.js | 87ms | 56ms | 25ms | 3rd |
| https://bordeaux.futurecdn.net/bordeaux.js | 84ms | 68ms | 13ms | 3rd |
| https://cdn.privacy-mgmt.com/unified/wrapperMessagingWithoutDetection.js | 74ms | 66ms | 3ms | 3rd |
A+Text CompressionAll text resources are compressedPASS
A+Font Loading2 fonts (57 KB)PASS
Web fonts
2
57 KB total
Render-blocking
0
of 2
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+Green HostingWhether the site is served from green-energy infrastructurePASS
Green Hosting
This site is hosted on green energy infrastructure
Provider: Cloudflare
AHTTP Cachingmax-age=14400 (4 hours)PASS
public, max-age=14400
| Directive | Value | Meaning |
|---|---|---|
| public | — | Any cache may store this response |
| max-age | 14400 | Cache for 4 hours |
Network Waterfall68 requests over 1628msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.sciencealert.com www.sciencealert.com | Other | 113ms | 37 KB | — | $2/mo | Optional |
Unattributable Unattributable | Other | 95ms | 0 KB | — | $1/mo | Optional |
cdn.taboola.com cdn.taboola.com | Other | 88ms | 326 KB | 64% | $1/mo | Optional |
6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app 6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app | Other | 87ms | 256 KB | 15% | $1/mo | Optional |
bordeaux.futurecdn.net bordeaux.futurecdn.net | Other | 84ms | 159 KB | 57% | $1/mo | Optional |
cdn.privacy-mgmt.com cdn.privacy-mgmt.com | Other | 74ms | 40 KB | — | $1/mo | Optional |
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
64% of cdn.taboola.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
57% of bordeaux.futurecdn.net'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