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.
1.11 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
4.97 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
24 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.
1.81 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.
5.02 s
Page Load Progression
FPage Weight BudgetAction5.9 MB transferred, 45 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
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
FJS BundlesAction11 scripts, 487 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtag/js?id=G-CSLL4ZEK4L&cx=c>m=4e64h1 | 147 KB | 106 KB (72%) | ✓ | 3rd |
| https://www.genome.gov/sites/default/files/js/js_wY7SbSc8raFRw1fRnmuVtinauFDQqI3EBpM2ZlZ-Jrw.js?scope=footer&delta=2&language=en&theme=nhgri&include=eJxljkEOgzAMBD8UmidZBkwwcmwUJ1B4fZEKl_a2O1qtBt2pAutCQ7USF3-tzWcYTCtphZ5EbAeeoEelEvBvXimvMPEbFLcwFDwPSik-ISSzJASoKEflweMvCJzXYhuNkJtUBie5viNnDzqnwnG6VHAnt0wPaSLdiok6Fx4vqy9OYj3KXRTVEopQOW5yttJ3kzUdsbLpB2MdYl8 | 110 KB | 86 KB (79%) | ✓ | 3rd |
| https://code.jquery.com/ui/1.12.1/jquery-ui.js | 122 KB | 75 KB (84%) | ✗ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-1GVMC3FXSC&cx=c>m=4e64h1 | 148 KB | 62 KB (41%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-CSLL4ZEK4L | 147 KB | 61 KB (42%) | ✓ | 3rd |
| https://www.genome.gov/sites/default/files/google_analytics/gtag.js?tdw9db | 124 KB | 61 KB (50%) | ✓ | 3rd |
| https://www.genome.gov/sites/default/files/js/js_xi0FtGdjW2Z6VR7E4ps29cMkIygxI-vuQpt3k_8ypz4.js?scope=footer&delta=0&language=en&theme=nhgri&include=eJxljkEOgzAMBD8UmidZBkwwcmwUJ1B4fZEKl_a2O1qtBt2pAutCQ7USF3-tzWcYTCtphZ5EbAeeoEelEvBvXimvMPEbFLcwFDwPSik-ISSzJASoKEflweMvCJzXYhuNkJtUBie5viNnDzqnwnG6VHAnt0wPaSLdiok6Fx4vqy9OYj3KXRTVEopQOW5yttJ3kzUdsbLpB2MdYl8 | 455 KB | 35 KB (8%) | ✓ | 3rd |
| https://script.crazyegg.com/pages/scripts/0097/2751.js | 0 KB | — | ✓ | 3rd |
| https://dap.digitalgov.gov/Universal-Federated-Analytics-Min.js?agency=HHS&subagency=NIH | 9 KB | — | ✓ | 3rd |
| https://dap.digitalgov.gov/web-vitals/dist/web-vitals.attribution.iife.js | 4 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 InventoryAction45 resources · 5.9 MB · 487 KB savings availableFIX
~486.8 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 45 resources | 5.9 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BImage Optimization23 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
CJS Execution CostAction1336ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.genome.gov/ | 480ms | 1ms | 0ms | 3rd |
| Unattributable | 421ms | 2ms | 0ms | 3rd |
| https://www.genome.gov/sites/default/files/js/js_xi0FtGdjW2Z6VR7E4ps29cMkIygxI-vuQpt3k_8ypz4.js?scope=footer&delta=0&language=en&theme=nhgri&include=eJxljkEOgzAMBD8UmidZBkwwcmwUJ1B4fZEKl_a2O1qtBt2pAutCQ7USF3-tzWcYTCtphZ5EbAeeoEelEvBvXimvMPEbFLcwFDwPSik-ISSzJASoKEflweMvCJzXYhuNkJtUBie5viNnDzqnwnG6VHAnt0wPaSLdiok6Fx4vqy9OYj3KXRTVEopQOW5yttJ3kzUdsbLpB2MdYl8 | 159ms | 83ms | 45ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-CSLL4ZEK4L | 77ms | 64ms | 12ms | 3rd |
| https://www.genome.gov/sites/default/files/google_analytics/gtag.js?tdw9db | 77ms | 56ms | 16ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-1GVMC3FXSC&cx=c>m=4e64h1 | 67ms | 55ms | 11ms | 3rd |
| https://www.genome.gov/sites/default/files/js/js_wY7SbSc8raFRw1fRnmuVtinauFDQqI3EBpM2ZlZ-Jrw.js?scope=footer&delta=2&language=en&theme=nhgri&include=eJxljkEOgzAMBD8UmidZBkwwcmwUJ1B4fZEKl_a2O1qtBt2pAutCQ7USF3-tzWcYTCtphZ5EbAeeoEelEvBvXimvMPEbFLcwFDwPSik-ISSzJASoKEflweMvCJzXYhuNkJtUBie5viNnDzqnwnG6VHAnt0wPaSLdiok6Fx4vqy9OYj3KXRTVEopQOW5yttJ3kzUdsbLpB2MdYl8 | 55ms | 33ms | 18ms | 3rd |
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 Loading1 fonts (42 KB)PASS
Web fonts
1
42 KB total
Render-blocking
0
of 1
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 Waterfall45 requests over 1642msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.genome.gov www.genome.gov | Other | 480ms | 40 KB | — | $6/mo | Costly |
Unattributable Unattributable | Other | 421ms | 0 KB | — | $6/mo | Costly |
www.genome.gov www.genome.gov | Other | 159ms | 455 KB | 8% | $2/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 77ms | 147 KB | 42% | $1/mo | Optional |
www.genome.gov www.genome.gov | Other | 77ms | 124 KB | 50% | $1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 67ms | 148 KB | 41% | $1/mo | Optional |
www.genome.gov www.genome.gov | Other | 55ms | 110 KB | 79% | $1/mo | Optional |
These scripts may cost more than they're worth
- www.genome.gov adds 480ms and costs ~$6/month
- Unattributable adds 421ms and costs ~$6/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.genome.gov takes 480ms 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 421ms 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
79% of www.genome.gov'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