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.
1.30 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
10.05 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
178 ms
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.
2.72 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.
10.59 s
Page Load Progression
FPage Weight BudgetAction17.2 MB transferred, 138 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
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
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
DPage Weight InventoryAction138 resources · 17.2 MB · 297 KB savings availableFIX
~297.3 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 138 resources | 17.2 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BImage Optimization63 images, 0 KB saveableREVIEW
CJS Execution CostAction1524ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.columbia.edu/content/sites/www.columbia.edu.content/files/js/js_-VfW5OTnd-614WcPt0EhMj80XeH_mO_fMqAs2ygFCfE.js?qs=9a87463107391083ae41a44cdd03a374 | 600ms | 413ms | 3ms | 3rd |
| Unattributable | 313ms | 53ms | 0ms | 3rd |
| https://www.columbia.edu/ | 285ms | 26ms | 8ms | 3rd |
| https://www.columbia.edu/cdn-cgi/challenge-platform/scripts/jsd/main.js | 121ms | 97ms | 1ms | 3rd |
| https://www.columbia.edu/content/sites/www.columbia.edu.content/files/js/js_iBsAvH-N2woJFVjmYPshSnQtRNgBdHjpEEZSo-7-tf4.js?qs=aca78062e4b4e688f8c9675aa5f2f24b | 85ms | 47ms | 20ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-09H1KYXPLX&cx=c>m=4e64k0h2 | 69ms | 55ms | 14ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=UA-18290390-1 | 52ms | 41ms | 10ms | 3rd |
CJS BundlesAction27 scripts, 297 KB unusedREVIEW
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.columbia.edu/content/sites/www.columbia.edu.content/files/js/js_NDpNdspfAthpa2cWemm86171HkiPGGIngLjnzYTxBmw.js?qs=168d8d191de5b5bf20f9320b672d955e | 134 KB | 73 KB (55%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-09H1KYXPLX&cx=c>m=4e64k0h2 | 158 KB | 63 KB (40%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=UA-18290390-1 | 116 KB | 63 KB (55%) | ✓ | 3rd |
| https://code.jquery.com/ui/1.12.1/jquery-ui.min.js | 66 KB | 59 KB (89%) | ✓ | 3rd |
| https://www.columbia.edu/content/sites/www.columbia.edu.content/files/js/js_iBsAvH-N2woJFVjmYPshSnQtRNgBdHjpEEZSo-7-tf4.js?qs=aca78062e4b4e688f8c9675aa5f2f24b | 64 KB | 39 KB (61%) | ✓ | 3rd |
| https://player.vimeo.com/api/player.js | 9 KB | — | ✓ | 3rd |
| https://www.youtube.com/s/player/218d9d92/www-widgetapi.vflset/www-widgetapi.js | 11 KB | — | ✓ | 3rd |
| https://www.columbia.edu/content/sites/www.columbia.edu.content/files/js/js_I-A3z7rZtEmcBCAxusPQUol24M3Ki6FwNQuIsUD8JNM.js?qs=e5d66f579508b6cf35d24ea5f38c9ed5 | 28 KB | — | ✓ | 3rd |
| https://www.columbia.edu/content/sites/www.columbia.edu.content/files/js/js_QB5AaDGtiMu0b6tu1gTogmvM6vnUE7jDKCBZuzPWkqo.js?qs=cad13804c17162889b2e4b2d7fe29170 | 4 KB | — | ✓ | 3rd |
| https://www.columbia.edu/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.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
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
A+Text CompressionAll text resources are compressedPASS
A+Font Loading16 fonts (621 KB)PASS
Web fonts
16
621 KB total
Render-blocking
0
of 16
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 ~6 KB and ~12 ms
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
Network Waterfall138 requests over 2521msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.columbia.edu www.columbia.edu | Other | 600ms | 32 KB | — | $8/mo | Costly |
Unattributable Unattributable | Other | 313ms | 0 KB | — | $4/mo | Costly |
www.columbia.edu www.columbia.edu | Other | 285ms | 44 KB | — | $4/mo | Costly |
www.columbia.edu www.columbia.edu | Other | 121ms | 0 KB | — | $2/mo | Optional |
www.columbia.edu www.columbia.edu | Other | 85ms | 64 KB | 61% | $1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 69ms | 158 KB | 40% | $1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 52ms | 116 KB | 55% | $1/mo | Optional |
These scripts may cost more than they're worth
- www.columbia.edu adds 600ms and costs ~$8/month
- Unattributable adds 313ms and costs ~$4/month
- www.columbia.edu adds 285ms 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.columbia.edu takes 600ms 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 313ms 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.columbia.edu takes 285ms 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
61% of www.columbia.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
55% 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