Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
C
Image Optimization
Action
30 images, 0 KB saveable
REVIEW
30 images, 0 KB saveable
Warning::
!
https://aap2.silverchair-cdn.com/data/SiteBuilderA... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://publications.aap.org/UI/app/svg/umbrella/u... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://aap2.silverchair-cdn.com/data/SiteBuilderA... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
30images408 KB
0oversized-0 KB
30legacy format
3missing dimensionsCLS risk
Set explicit width and height to prevent CLS.
Why this matters
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.
Why this matters
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.
Why this matters
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW
Green Hosting
No green hosting detected
A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
✓
All text resources are compressed
All text resources are properly compressed.
A+
Font Loading
4 fonts (106 KB)
PASS
4 fonts (106 KB)
Info::
i
4 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
4
106 KB total
Render-blocking
0
of 4
Dominant font-display
swap
Most common across fonts
Font loading timeline
TransferFOIT (block)FOUT (swap)
5aUu9_-1phKLFgshYDvh6Vw...woff2swap
Size17 KB
Load time27 ms
Start1.9 s
RiskFOUT — text flashes from fallback to web font
memvYaGs126MiZpBA-UvWbX...woff2swap
Size42 KB
Load time56 ms
Start1.9 s
RiskFOUT — text flashes from fallback to web font
aap2.ttfttfswap
Size31 KB
Load time9 ms
Start1.9 s
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
5aUz9_-1phKLFgshYDvh6Vw...woff2swap
Size17 KB
Load time47 ms
Start1.9 s
RiskFOUT — text flashes from fallback to web font
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 ~9 KB and ~18 ms
A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
✓
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
✓
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
✓
No resource hint issues
A+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
✓
No render-blocking resources detected in <head>
A+
Third-Party Resources
No third-party resources detected
PASS
No third-party resources detected
Network Waterfall
106 requests over 18947ms
INFO
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
100%of JavaScript execution is third-party
First-party Third-party4677ms · 1463KB · $62/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
Unattributable
Unattributable
Other
1180ms
0 KB
—
$16/mo
Costly
ajax.googleapis.com
ajax.googleapis.com
Other
446ms
31 KB
—
$6/mo
Costly
publications.aap.org
publications.aap.org
Other
430ms
11 KB
—
$6/mo
Costly
jsDelivr
cdn.jsdelivr.net
CDN
398ms
251 KB
49%
$5/mo
Costly
cdn.userway.org
cdn.userway.org
Other
294ms
39 KB
53%
$4/mo
Costly
aap2.silverchair-cdn.com
aap2.silverchair-cdn.com
Other
260ms
137 KB
79%
$3/mo
Costly
publications.aap.org
publications.aap.org
Other
258ms
0 KB
—
$3/mo
Costly
securepubads.g.doubleclick.net
securepubads.g.doubleclick.net
Other
239ms
188 KB
58%
$3/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
211ms
151 KB
43%
$3/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
203ms
152 KB
44%
$3/mo
Costly
cdn.userway.org
cdn.userway.org
Other
195ms
48 KB
57%
$3/mo
Optional
Google Tag Manager
www.googletagmanager.com
Tag Manager
118ms
119 KB
53%
$2/mo
Optional
aap.hum.works
aap.hum.works
Other
116ms
104 KB
44%
$2/mo
Optional
Google Tag Manager
www.googletagmanager.com
Tag Manager
83ms
113 KB
58%
$1/mo
Optional
securepubads.g.doubleclick.net
securepubads.g.doubleclick.net
Other
77ms
34 KB
—
$1/mo
Optional
cdn.userway.org
cdn.userway.org
Other
62ms
14 KB
—
$1/mo
Optional
platform-api.sharethis.com
platform-api.sharethis.com
Other
54ms
47 KB
59%
$1/mo
Optional
pagead2.googlesyndication.com
pagead2.googlesyndication.com
Other
53ms
25 KB
—
$1/mo
Optional
Unattributable
Other
Costly
Execution1180ms
Transfer0 KB
Monthly Cost$16/mo
ajax.googleapis.com
Other
Costly
Execution446ms
Transfer31 KB
Monthly Cost$6/mo
publications.aap.org
Other
Costly
Execution430ms
Transfer11 KB
Monthly Cost$6/mo
jsDelivr
CDN
Costly
Execution398ms
Transfer251 KB
Unused49%
Monthly Cost$5/mo
cdn.userway.org
Other
Costly
Execution294ms
Transfer39 KB
Unused53%
Monthly Cost$4/mo
aap2.silverchair-cdn.com
Other
Costly
Execution260ms
Transfer137 KB
Unused79%
Monthly Cost$3/mo
publications.aap.org
Other
Costly
Execution258ms
Transfer0 KB
Monthly Cost$3/mo
securepubads.g.doubleclick.net
Other
Costly
Execution239ms
Transfer188 KB
Unused58%
Monthly Cost$3/mo
Google Tag Manager
Tag Manager
Costly
Execution211ms
Transfer151 KB
Unused43%
Monthly Cost$3/mo
Google Tag Manager
Tag Manager
Costly
Execution203ms
Transfer152 KB
Unused44%
Monthly Cost$3/mo
cdn.userway.org
Other
Optional
Execution195ms
Transfer48 KB
Unused57%
Monthly Cost$3/mo
Google Tag Manager
Tag Manager
Optional
Execution118ms
Transfer119 KB
Unused53%
Monthly Cost$2/mo
aap.hum.works
Other
Optional
Execution116ms
Transfer104 KB
Unused44%
Monthly Cost$2/mo
Google Tag Manager
Tag Manager
Optional
Execution83ms
Transfer113 KB
Unused58%
Monthly Cost$1/mo
securepubads.g.doubleclick.net
Other
Optional
Execution77ms
Transfer34 KB
Monthly Cost$1/mo
cdn.userway.org
Other
Optional
Execution62ms
Transfer14 KB
Monthly Cost$1/mo
platform-api.sharethis.com
Other
Optional
Execution54ms
Transfer47 KB
Unused59%
Monthly Cost$1/mo
pagead2.googlesyndication.com
Other
Optional
Execution53ms
Transfer25 KB
Monthly Cost$1/mo
These scripts may cost more than they're worth
Unattributable adds 1180ms and costs ~$16/month
ajax.googleapis.com adds 446ms and costs ~$6/month
publications.aap.org adds 430ms and costs ~$6/month
jsDelivr adds 398ms and costs ~$5/month
cdn.userway.org adds 294ms and costs ~$4/month
aap2.silverchair-cdn.com adds 260ms and costs ~$3/month
publications.aap.org adds 258ms and costs ~$3/month
securepubads.g.doubleclick.net adds 239ms and costs ~$3/month
Google Tag Manager adds 211ms and costs ~$3/month
Google Tag Manager adds 203ms and costs ~$3/month
100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.
Why this matters
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 1180ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
ajax.googleapis.com takes 446ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
publications.aap.org takes 430ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
jsDelivr takes 398ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
cdn.userway.org takes 294ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
53% of cdn.userway.org's code is unused. The script may be loading features you don't use.
Why this matters
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
aap2.silverchair-cdn.com takes 260ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
79% of aap2.silverchair-cdn.com's code is unused. The script may be loading features you don't use.
Why this matters
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
publications.aap.org takes 258ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
securepubads.g.doubleclick.net takes 239ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
58% of securepubads.g.doubleclick.net's code is unused. The script may be loading features you don't use.
Why this matters
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
Google Tag Manager takes 211ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
Google Tag Manager takes 203ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
Why this matters
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
57% of cdn.userway.org's code is unused. The script may be loading features you don't use.
Why this matters
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
53% of Google Tag Manager's code is unused. The script may be loading features you don't use.
Why this matters
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
58% of Google Tag Manager's code is unused. The script may be loading features you don't use.
Why this matters
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
59% of platform-api.sharethis.com's code is unused. The script may be loading features you don't use.
Why this matters
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.