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.
1.01 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
4.43 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
626 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.025
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
3.97 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.
13.07 s
Page Load Progression
803 ms 1.6 s
2.4 s
3.2 s
4.0 s
4.8 s 5.6 s
6.4 sFPage Weight BudgetAction38.0 MB transferred, 203 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
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
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
FJS Execution CostAction5168ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.southwest.com/resources/c76dc01aee548ff55d184615dd91bee22130011c85bd8 | 2036ms | 1813ms | 14ms | 3rd |
| https://www.southwest.com/ | 1176ms | 840ms | 1ms | 3rd |
| Unattributable | 950ms | 92ms | 0ms | 3rd |
| https://www.southwest.com/v2/landing/home-page/static/25.0.1/js/app-dcb821d8.js | 280ms | 266ms | 9ms | 3rd |
| https://cdn.quantummetric.com/qscripts/quantum-southwest.js | 231ms | 218ms | 10ms | 3rd |
| https://www.southwest.com/swa-resources/scripts/analytics/analytics.js | 161ms | 114ms | 38ms | 3rd |
| https://www.southwest.com/assets/app/scripts/swa-common.js | 126ms | 111ms | 13ms | 3rd |
| https://cdn.cookielaw.org/scripttemplates/202410.1.0/otBannerSdk.js | 83ms | 57ms | 14ms | 3rd |
| https://www.southwest.com/v2/landing/home-page/static/25.0.1/js/vendor-49d0a293.js | 64ms | 24ms | 5ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=DC-8601678&cx=c>m=4e64e1 | 61ms | 49ms | 12ms | 3rd |
FJS BundlesAction83 scripts, 681 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.southwest.com/v2/landing/home-page/static/25.0.1/js/app-e96e9bea.js | 238 KB | 118 KB (50%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=DC-8601678&cx=c>m=4e64e1 | 129 KB | 61 KB (47%) | ✓ | 3rd |
| https://cdn.cookielaw.org/scripttemplates/202410.1.0/otBannerSdk.js | 112 KB | 61 KB (55%) | ✓ | 3rd |
| https://www.southwest.com/v2/landing/home-page/static/25.0.1/js/app-111e1271.js | 133 KB | 60 KB (45%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-826888480 | 144 KB | 48 KB (34%) | ✓ | 3rd |
| https://www.southwest.com/v2/landing/home-page/static/25.0.1/js/app-dcb821d8.js | 84 KB | 47 KB (57%) | ✓ | 3rd |
| https://cdn.quantummetric.com/qscripts/quantum-southwest.js | 119 KB | 46 KB (39%) | ✓ | 3rd |
| https://www.southwest.com/swa-resources/scripts/analytics/analytics.js | 183 KB | 40 KB (22%) | ✓ | 3rd |
| https://www.southwest.com/v2/landing/home-page/static/25.0.1/js/vendor-49d0a293.js | 54 KB | 31 KB (58%) | ✓ | 3rd |
| https://aswpsdkus.com/notify/v2/ua-sdk.min.js | 63 KB | 31 KB (50%) | ✓ | 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 InventoryAction203 resources · 38.0 MB · 681 KB savings availableFIX
~681.1 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 203 resources | 38.0 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction45 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
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 Loading2 fonts (64 KB)PASS
Web fonts
2
64 KB total
Render-blocking
0
of 2
Dominant font-display
swap
Most common across fonts
Font loading timeline
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
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)
Fixing the unchecked items could save ~19 KB and ~38 ms
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
Network Waterfall203 requests over 9116msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.southwest.com www.southwest.com | Other | 2036ms | 79 KB | — | $27/mo | Costly |
www.southwest.com www.southwest.com | Other | 1176ms | 4 KB | — | $16/mo | Costly |
Unattributable Unattributable | Other | 950ms | 0 KB | — | $13/mo | Costly |
www.southwest.com www.southwest.com | Other | 280ms | 84 KB | 57% | $4/mo | Costly |
cdn.quantummetric.com cdn.quantummetric.com | Other | 231ms | 119 KB | 39% | $3/mo | Costly |
www.southwest.com www.southwest.com | Other | 161ms | 183 KB | 22% | $2/mo | Optional |
www.southwest.com www.southwest.com | Other | 126ms | 240 KB | — | $2/mo | Optional |
OneTrust cdn.cookielaw.org | Consent | 83ms | 112 KB | 55% | $1/mo | Essential |
www.southwest.com www.southwest.com | Other | 64ms | 54 KB | 58% | $1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 61ms | 129 KB | 47% | $1/mo | Optional |
These scripts may cost more than they're worth
- www.southwest.com adds 2036ms and costs ~$27/month
- www.southwest.com adds 1176ms and costs ~$16/month
- Unattributable adds 950ms and costs ~$13/month
- www.southwest.com adds 280ms and costs ~$4/month
- cdn.quantummetric.com 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
www.southwest.com takes 2036ms 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.southwest.com takes 1176ms 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 950ms 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.southwest.com takes 280ms 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
57% of www.southwest.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
cdn.quantummetric.com 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
55% of OneTrust'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
58% of www.southwest.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