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.
1.28 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
2.27 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
60 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.083
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
2.30 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.
4.07 s
Page Load Progression
FPage Weight BudgetAction18.6 MB transferred, 61 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
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
CSS bundle is large — purge unused styles (PurgeCSS, Tailwind JIT) to reduce CSS payload.
Source: web.dev
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
DPage Weight InventoryAction61 resources · 18.6 MB · 208 KB savings availableFIX
~208.5 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 61 resources | 18.6 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BImage Optimization14 images, 0 KB saveableREVIEW
Set explicit width and height to prevent CLS.
Performance issues directly impact user engagement and conversion rates.
CJS Execution CostAction1036ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.swarthmore.edu/ | 317ms | 2ms | 0ms | 3rd |
| https://www.swarthmore.edu/sites/default/files/js/js_fWKh1eMp9sgrPnNXPtIuZLSCULDTl14zm1SSFM-le64.js?scope=footer&delta=0&language=en&theme=swarthmore&include=eJxLz89Pz0mNL0lM108HEjrpqHy9xKzEClTBXJ3i8sSikozc_KJU_fSc_KTEHCSR-MTkxJz8dP3i5KLMghIAvXgkqA | 310ms | 179ms | 17ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-LTWLTXJTKP&cx=c>m=4e64k1 | 138ms | 122ms | 13ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-M8XQCCG | 134ms | 118ms | 14ms | 3rd |
| Unattributable | 75ms | 2ms | 0ms | 3rd |
| https://www.swarthmore.edu/sites/default/files/css/css_nRToGU55zYfMKlADeYgEJUDcPhZ0VGt9T8yQFKNsxFo.css?delta=1&language=en&theme=swarthmore&include=eJxFy0sKwCAMRdENia7pWYNaYg2J9rP70kLp5A4O3KUrhaRTwB4rTidQZIUU-_gXPzeZkasVSs4O6Cjt-TP3CHZ22aAWIozcXumw8Na3nibTDafxKYU | 61ms | 0ms | 0ms | 3rd |
CJS BundlesAction18 scripts, 208 KB unusedREVIEW
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.swarthmore.edu/sites/default/files/js/js_fWKh1eMp9sgrPnNXPtIuZLSCULDTl14zm1SSFM-le64.js?scope=footer&delta=0&language=en&theme=swarthmore&include=eJxLz89Pz0mNL0lM108HEjrpqHy9xKzEClTBXJ3i8sSikozc_KJU_fSc_KTEHCSR-MTkxJz8dP3i5KLMghIAvXgkqA | 147 KB | 73 KB (50%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-M8XQCCG | 142 KB | 68 KB (48%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-LTWLTXJTKP&cx=c>m=4e64k1 | 155 KB | 67 KB (43%) | ✓ | 3rd |
| https://www.youtube-nocookie.com/s/player/1bb6ee63/player_embed_es6.vflset/en_US/base.js | 436 KB | — | ✓ | 3rd |
| https://www.youtube.com/player_api | 4 KB | — | ✓ | 3rd |
| https://f.vimeocdn.com/p/4.46.43/js/player.module.js | 211 KB | — | ✓ | 3rd |
| https://f.vimeocdn.com/p/4.46.43/js/vendor.module.js | 93 KB | — | ✓ | 3rd |
| https://www.youtube.com/s/_/ytembeds/_/js/k=ytembeds.base.en_US.5f0apfZzpOA.2021.O/am=AAAABA/d=1/br=1/rs=AGKMywFg3MG1UeKh8ePjbhY_YEMv-NHjmA/m=root,base | 140 KB | — | ✓ | 3rd |
| https://www.swarthmore.edu/sites/default/files/js/js_giSujFfue2N36iWEbjqffm83IOB-kERM5_14MCtzw7Q.js?scope=header&delta=0&language=en&theme=swarthmore&include=eJxLz89Pz0mNL0lM108HEjrpqHy9xKzEClTBXJ3i8sSikozc_KJU_fSc_KTEHCSR-MTkxJz8dP3i5KLMghIAvXgkqA | 1 KB | — | ✓ | 3rd |
| https://player.vimeo.com/api/player.js | 9 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
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 Loading4 fonts (165 KB)PASS
Web fonts
4
165 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
Network Waterfall61 requests over 4314msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.swarthmore.edu www.swarthmore.edu | Other | 317ms | 29 KB | — | $4/mo | Costly |
www.swarthmore.edu www.swarthmore.edu | Other | 310ms | 147 KB | 50% | $4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 138ms | 155 KB | 43% | $2/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 134ms | 142 KB | 48% | $2/mo | Optional |
Unattributable Unattributable | Other | 75ms | 0 KB | — | $1/mo | Optional |
www.swarthmore.edu www.swarthmore.edu | Other | 61ms | 82 KB | — | $1/mo | Optional |
These scripts may cost more than they're worth
- www.swarthmore.edu adds 317ms and costs ~$4/month
- www.swarthmore.edu adds 310ms and costs ~$4/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.swarthmore.edu takes 317ms 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.swarthmore.edu takes 310ms 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
50% of www.swarthmore.edu'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