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.
2.79 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
8.36 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
6.21 s
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.297
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
4.98 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.
16.17 s
Page Load Progression
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
FJS Execution CostAction12559ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/gl-particles.js | 9287ms | 330ms | 0ms | 3rd |
| Unattributable | 1117ms | 395ms | 0ms | 3rd |
| https://www.windy.com/ | 905ms | 442ms | 2ms | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/leaflet-gl.js | 507ms | 356ms | 2ms | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/index.js | 402ms | 281ms | 2ms | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/_shared-misc.js | 250ms | 38ms | 0ms | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/_shared-effects.js | 90ms | 46ms | 0ms | 3rd |
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction11 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
BJS Bundles48 scripts, 83 KB unusedREVIEW
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.windy.com/v/49.1.1.ind.eb7f/leaflet-gl.js | 101 KB | 52 KB (52%) | ✓ | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/index.js | 108 KB | 31 KB (28%) | ✓ | 3rd |
| https://www.windy.com/patch/v9/patch.js?refTime=2026-04-21T20:55 | 0 KB | — | ✓ | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/mobile-ui.js | 3 KB | — | ✓ | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/search-input.js | 5 KB | — | ✓ | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/startup-weather.js | 5 KB | — | ✓ | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/_shared-misc.js | 5 KB | — | ✓ | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/_shared-legacy.js | 0 KB | — | ✓ | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/_shared-effects.js | 10 KB | — | ✓ | 3rd |
| https://www.windy.com/v/49.1.1.ind.eb7f/plugins/_shared-if.js | 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
A+Page Weight Budget698 KB transferred, 183 requestsPASS
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
A+Text CompressionAll text resources are compressedPASS
A+Font Loading2 fonts (32 KB)PASS
Web fonts
2
32 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 Hints10 hints, 0 missing preconnectsPASS
Current Resource Hints
10 resource hints configured
APage Weight Inventory183 resources · 698 KB · 83 KB savings availablePASS
~82.9 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 183 resources | 697.9 KiB | ||||||
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: Google Cloud
Network Waterfall183 requests over 1303msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.windy.com www.windy.com | Other | 9287ms | 9 KB | — | $123/mo | Costly |
Unattributable Unattributable | Other | 1117ms | 0 KB | — | $15/mo | Costly |
www.windy.com www.windy.com | Other | 905ms | 2 KB | — | $12/mo | Costly |
www.windy.com www.windy.com | Other | 507ms | 101 KB | 52% | $7/mo | Costly |
www.windy.com www.windy.com | Other | 402ms | 108 KB | 28% | $5/mo | Costly |
www.windy.com www.windy.com | Other | 250ms | 5 KB | — | $3/mo | Costly |
www.windy.com www.windy.com | Other | 90ms | 10 KB | — | $1/mo | Optional |
These scripts may cost more than they're worth
- www.windy.com adds 9287ms and costs ~$123/month
- Unattributable adds 1117ms and costs ~$15/month
- www.windy.com adds 905ms and costs ~$12/month
- www.windy.com adds 507ms and costs ~$7/month
- www.windy.com adds 402ms and costs ~$5/month
- www.windy.com adds 250ms 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.windy.com takes 9287ms 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 1117ms 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.windy.com takes 905ms 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.windy.com takes 507ms 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 www.windy.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
www.windy.com takes 402ms 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.windy.com takes 250ms 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