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
71 images, 0 KB saveable
REVIEW
71 images, 0 KB saveable
Warning::
!
https://www.usps.com/assets/images/home/stamps.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/footer/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/hamburger.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/schedule_p... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/holdmail.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/featured_c... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/welcome/feature... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/welcome/carouse... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/po_box.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/free_boxes... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/footer/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/search.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/location.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/calculate_... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/welcome/premium... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/footer/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/welcome/feature... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/hs-code-se... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/footer/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/logo_mobil... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/find_zip.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/header/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/footer/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/welcome/feature... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/header/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/tracking.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/campaigns/postm... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/welcome/feature... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/footer/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/home/change_add... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/global-elements/header/images... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://beacon.lynx.cognitivlabs.com/pixel/capture... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.usps.com/assets/images/welcome/feature... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
71images4.1 MB
0oversized-0 KB
69legacy format
33missing 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
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
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
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
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
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
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
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
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
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
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
3 fonts (156 KB)
PASS
3 fonts (156 KB)
Info::
i
3 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
3
156 KB total
Render-blocking
0
of 3
Dominant font-display
swap
Most common across fonts
Font loading timeline
TransferFOIT (block)FOUT (swap)
d5af76d8-a90b-4527-b3a3...woffswap
Size58 KB
Load time78 ms
Start619 ms
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
4a9c62ab-b359-4081-8383...woffswap
Size46 KB
Load time59 ms
Start619 ms
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
5b4a262e-3342-44e2-8ad7...woffswap
Size51 KB
Load time47 ms
Start701 ms
RiskFOUT — text flashes from fallback to web font
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 ~47 KB and ~94 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
154 requests over 4076ms
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-party5025ms · 1072KB · $29/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
Unattributable
Unattributable
Other
983ms
0 KB
—
$6/mo
Costly
www.usps.com
www.usps.com
Other
885ms
1 KB
22%
$5/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
541ms
210 KB
32%
$3/mo
Costly
www.usps.com
www.usps.com
Other
532ms
23 KB
—
$3/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
507ms
161 KB
36%
$3/mo
Costly
Facebook Pixel
connect.facebook.net
Advertising
246ms
127 KB
29%
$1/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
242ms
129 KB
50%
$1/mo
Costly
sc-static.net
sc-static.net
Other
192ms
25 KB
—
$1/mo
Optional
www.usps.com
www.usps.com
Other
178ms
30 KB
68%
$1/mo
Optional
Facebook Pixel
connect.facebook.net
Advertising
158ms
96 KB
35%
$1/mo
Optional
Google Tag Manager
www.googletagmanager.com
Tag Manager
120ms
141 KB
45%
$1/mo
Optional
c.tvpixel.com
c.tvpixel.com
Other
111ms
32 KB
—
$1/mo
Optional
LinkedIn Insight
snap.licdn.com
Advertising
97ms
19 KB
—
$1/mo
Optional
cdn.boomtrain.com
cdn.boomtrain.com
Other
89ms
31 KB
—
$1/mo
Optional
s.pinimg.com
s.pinimg.com
Other
78ms
27 KB
—
$0/mo
Optional
www.redditstatic.com
www.redditstatic.com
Other
65ms
19 KB
—
$0/mo
Optional
Unattributable
Other
Costly
Execution983ms
Transfer0 KB
Monthly Cost$6/mo
www.usps.com
Other
Costly
Execution885ms
Transfer1 KB
Unused22%
Monthly Cost$5/mo
Google Tag Manager
Tag Manager
Costly
Execution541ms
Transfer210 KB
Unused32%
Monthly Cost$3/mo
www.usps.com
Other
Costly
Execution532ms
Transfer23 KB
Monthly Cost$3/mo
Google Tag Manager
Tag Manager
Costly
Execution507ms
Transfer161 KB
Unused36%
Monthly Cost$3/mo
Facebook Pixel
Advertising
Costly
Execution246ms
Transfer127 KB
Unused29%
Monthly Cost$1/mo
Google Tag Manager
Tag Manager
Costly
Execution242ms
Transfer129 KB
Unused50%
Monthly Cost$1/mo
sc-static.net
Other
Optional
Execution192ms
Transfer25 KB
Monthly Cost$1/mo
www.usps.com
Other
Optional
Execution178ms
Transfer30 KB
Unused68%
Monthly Cost$1/mo
Facebook Pixel
Advertising
Optional
Execution158ms
Transfer96 KB
Unused35%
Monthly Cost$1/mo
Google Tag Manager
Tag Manager
Optional
Execution120ms
Transfer141 KB
Unused45%
Monthly Cost$1/mo
c.tvpixel.com
Other
Optional
Execution111ms
Transfer32 KB
Monthly Cost$1/mo
LinkedIn Insight
Advertising
Optional
Execution97ms
Transfer19 KB
Monthly Cost$1/mo
cdn.boomtrain.com
Other
Optional
Execution89ms
Transfer31 KB
Monthly Cost$1/mo
s.pinimg.com
Other
Optional
Execution78ms
Transfer27 KB
Monthly Cost$0/mo
www.redditstatic.com
Other
Optional
Execution65ms
Transfer19 KB
Monthly Cost$0/mo
These scripts may cost more than they're worth
Unattributable adds 983ms and costs ~$6/month
www.usps.com adds 885ms and costs ~$5/month
Google Tag Manager adds 541ms and costs ~$3/month
www.usps.com adds 532ms and costs ~$3/month
Google Tag Manager adds 507ms and costs ~$3/month
Facebook Pixel adds 246ms and costs ~$1/month
Google Tag Manager adds 242ms and costs ~$1/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 983ms 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
www.usps.com takes 885ms 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 541ms 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
www.usps.com takes 532ms 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 507ms 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
Facebook Pixel takes 246ms 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 242ms 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
50% 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
68% of www.usps.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.
375 ms
750 ms
1.1 s
1.5 s