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.
5.03 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
18.83 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
3.86 s
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.053
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
6.89 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.
19.47 s
Page Load Progression
597 ms
1.2 s
1.8 s 2.4 s
3.0 s
3.6 s
4.2 s
4.8 sDPage Weight BudgetAction2.5 MB transferred, 148 requestsFIX
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
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 ImpactAction98% third-party, 0 ms blockingFIX
FJS Execution CostAction12047ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://jamanetwork.com/ | 2150ms | 93ms | 11ms | 1st |
| Unattributable | 1756ms | 597ms | 0ms | 3rd |
| https://cdn.quantummetric.com/qscripts/quantum-ama.js | 1067ms | 949ms | 49ms | 3rd |
| https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604200101/pubads_impl.js?cb=31097964 | 837ms | 666ms | 87ms | 3rd |
| https://r451.jamanetwork.com/script.js | 799ms | 737ms | 18ms | 3rd |
| https://cdn.jamanetwork.com/UI/app/vendor/jquery-3.4.1.min.js?v=639102344110797911 | 633ms | 459ms | 16ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-WNKSNP | 589ms | 469ms | 82ms | 3rd |
| https://jamanetwork.com/cdn-cgi/challenge-platform/scripts/jsd/main.js | 546ms | 523ms | 8ms | 1st |
| https://api.b2c.com/api/init-3133s13tyvo448eled2.js | 505ms | 473ms | 3ms | 3rd |
| https://api.b2c.com/api/init-384qixmcp2s94lcpe6l.js?journal=jamanetw | 433ms | 386ms | 2ms | 3rd |
Showing top 10 of 23 scripts
FJS BundlesAction34 scripts, 605 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604200101/pubads_impl.js?cb=31097964 | 188 KB | 99 KB (53%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-NGYQD9R7ZM&cx=c>m=4e64h1 | 170 KB | 68 KB (40%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-CXRFQ9PGSH&cx=c>m=4e64h1 | 158 KB | 65 KB (41%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-B4FWHWKMEB&cx=c>m=4e64h1 | 158 KB | 64 KB (41%) | ✓ | 3rd |
| https://cdn.cookielaw.org/scripttemplates/202503.1.0/otBannerSdk.js | 116 KB | 61 KB (53%) | ✓ | 3rd |
| https://cdn.jamanetwork.com/UI/app/dist/app.min.js?v=639116193382194938 | 84 KB | 56 KB (67%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-WNKSNP | 149 KB | 51 KB (34%) | ✓ | 3rd |
| https://pagead2.googlesyndication.com/pagead/managed/js/activeview/current/ufs_web_display.js | 73 KB | 33 KB (46%) | ✓ | 3rd |
| https://cdn.quantummetric.com/qscripts/quantum-ama.js | 110 KB | 32 KB (29%) | ✓ | 3rd |
| https://r451.jamanetwork.com/plugin/library/a53ed3a366a92f652159978c3de3f6ef | 49 KB | 30 KB (61%) | ✓ | 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 InventoryAction148 resources · 2.5 MB · 605 KB savings availableFIX
~605.3 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 148 resources | 2.5 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction20 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
A+Text CompressionAll text resources are compressedPASS
A+Font Loading14 fonts (358 KB)PASS
Web fonts
14
358 KB total
Render-blocking
0
of 14
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
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- 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 ~107 KB and ~214 ms
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
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: Cloudflare
Network Waterfall148 requests over 6205msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
Unattributable Unattributable | Other | 1756ms | 0 KB | — | $23/mo | Costly |
cdn.quantummetric.com cdn.quantummetric.com | Other | 1067ms | 110 KB | 29% | $14/mo | Costly |
securepubads.g.doubleclick.net securepubads.g.doubleclick.net | Other | 837ms | 188 KB | 53% | $11/mo | Costly |
r451.jamanetwork.com r451.jamanetwork.com | Other | 799ms | 42 KB | — | $11/mo | Costly |
cdn.jamanetwork.com cdn.jamanetwork.com | Other | 633ms | 31 KB | — | $8/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 589ms | 149 KB | 34% | $8/mo | Costly |
api.b2c.com api.b2c.com | Other | 505ms | 7 KB | — | $7/mo | Costly |
api.b2c.com api.b2c.com | Other | 433ms | 7 KB | — | $6/mo | Costly |
OneTrust cdn.cookielaw.org | Consent | 357ms | 116 KB | 53% | $5/mo | Essential |
Google Tag Manager www.googletagmanager.com | Tag Manager | 354ms | 158 KB | 41% | $5/mo | Costly |
pagead2.googlesyndication.com pagead2.googlesyndication.com | Other | 324ms | 73 KB | 46% | $4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 309ms | 158 KB | 41% | $4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 268ms | 170 KB | 40% | $4/mo | Costly |
securepubads.g.doubleclick.net securepubads.g.doubleclick.net | Other | 259ms | 17 KB | — | $3/mo | Costly |
securepubads.g.doubleclick.net securepubads.g.doubleclick.net | Other | 207ms | 34 KB | 72% | $3/mo | Costly |
cdn.jamanetwork.com cdn.jamanetwork.com | Other | 196ms | 84 KB | 67% | $3/mo | Optional |
cdn.jamanetwork.com cdn.jamanetwork.com | Other | 130ms | 0 KB | — | $2/mo | Optional |
cdn.jamanetwork.com cdn.jamanetwork.com | Other | 125ms | 5 KB | — | $2/mo | Optional |
OneTrust cdn.cookielaw.org | Consent | 82ms | 9 KB | — | $1/mo | Essential |
ep2.adtrafficquality.google ep2.adtrafficquality.google | Other | 67ms | 8 KB | — | $1/mo | Optional |
plugins.blueconic.net plugins.blueconic.net | Other | 55ms | 30 KB | 74% | $1/mo | Optional |
These scripts may cost more than they're worth
- Unattributable adds 1756ms and costs ~$23/month
- cdn.quantummetric.com adds 1067ms and costs ~$14/month
- securepubads.g.doubleclick.net adds 837ms and costs ~$11/month
- r451.jamanetwork.com adds 799ms and costs ~$11/month
- cdn.jamanetwork.com adds 633ms and costs ~$8/month
- Google Tag Manager adds 589ms and costs ~$8/month
- api.b2c.com adds 505ms and costs ~$7/month
- api.b2c.com adds 433ms and costs ~$6/month
- Google Tag Manager adds 354ms and costs ~$5/month
- pagead2.googlesyndication.com adds 324ms and costs ~$4/month
- Google Tag Manager adds 309ms and costs ~$4/month
- Google Tag Manager adds 268ms and costs ~$4/month
- securepubads.g.doubleclick.net adds 259ms and costs ~$3/month
- securepubads.g.doubleclick.net adds 207ms and costs ~$3/month
78% 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
Unattributable takes 1756ms 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
cdn.quantummetric.com takes 1067ms 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
securepubads.g.doubleclick.net takes 837ms 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
53% of securepubads.g.doubleclick.net'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
r451.jamanetwork.com takes 799ms 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
cdn.jamanetwork.com takes 633ms 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
Google Tag Manager takes 589ms 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
api.b2c.com takes 505ms 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
api.b2c.com takes 433ms 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
53% 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
Google Tag Manager takes 354ms 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
pagead2.googlesyndication.com takes 324ms 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
Google Tag Manager takes 309ms 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
Google Tag Manager takes 268ms 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
securepubads.g.doubleclick.net takes 259ms 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
securepubads.g.doubleclick.net takes 207ms 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
72% of securepubads.g.doubleclick.net'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
67% of cdn.jamanetwork.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
74% of plugins.blueconic.net'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