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
16 images, 0 KB saveable
REVIEW
16 images, 0 KB saveable
Warning::
!
https://www.ornl.gov/themes/custom/ornl/images/orn... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.ornl.gov/themes/custom/ornl/images/doe... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.ornl.gov/themes/custom/ornl/images/bat... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
16images10.8 MB
0oversized-0 KB
16legacy 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
7 fonts (189 KB)
PASS
7 fonts (189 KB)
Info::
i
7 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
7
189 KB total
Render-blocking
0
of 7
Dominant font-display
swap
Most common across fonts
Font loading timeline
TransferFOIT (block)FOUT (swap)
KFO7CnqEu92Fr1ME7kSn66a...woff2swap
Size37 KB
Load time10 ms
Start338 ms
RiskFOUT — text flashes from fallback to web font
memvYaGs126MiZpBA-UvWbX...woff2swap
Size42 KB
Load time24 ms
Start338 ms
RiskFOUT — text flashes from fallback to web font
S6u9w4BMUTPHh6UVSwiPGQ3...woff2swap
Size14 KB
Load time27 ms
Start338 ms
RiskFOUT — text flashes from fallback to web font
S6uyw4BMUTPHjx4wXiWtFCc...woff2swap
Size14 KB
Load time31 ms
Start339 ms
RiskFOUT — text flashes from fallback to web font
memtYaGs126MiZpBA-UFUIc...woff2swap
Size44 KB
Load time33 ms
Start339 ms
RiskFOUT — text flashes from fallback to web font
KFO7CnqEu92Fr1ME7kSn66a...woff2swap
Size16 KB
Load time18 ms
Start339 ms
RiskFOUT — text flashes from fallback to web font
memvYaGs126MiZpBA-UvWbX...woff2swap
Size22 KB
Load time28 ms
Start340 ms
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)
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
61 requests over 1391ms
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-party2774ms · 899KB · $37/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
Unattributable
Unattributable
Other
692ms
0 KB
—
$9/mo
Costly
www.ornl.gov
www.ornl.gov
Other
533ms
15 KB
—
$7/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
286ms
147 KB
42%
$4/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
250ms
158 KB
39%
$3/mo
Costly
www.ornl.gov
www.ornl.gov
Other
231ms
1 KB
—
$3/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
200ms
119 KB
52%
$3/mo
Costly
use.fontawesome.com
use.fontawesome.com
Other
143ms
248 KB
—
$2/mo
Optional
dap.digitalgov.gov
dap.digitalgov.gov
Other
107ms
4 KB
—
$1/mo
Optional
siteimproveanalytics.com
siteimproveanalytics.com
Other
100ms
21 KB
—
$1/mo
Optional
Google Tag Manager
www.googletagmanager.com
Tag Manager
88ms
147 KB
72%
$1/mo
Optional
www.ornl.gov
www.ornl.gov
Other
82ms
4 KB
—
$1/mo
Optional
www.ornl.gov
www.ornl.gov
Other
61ms
35 KB
—
$1/mo
Optional
Unattributable
Other
Costly
Execution692ms
Transfer0 KB
Monthly Cost$9/mo
www.ornl.gov
Other
Costly
Execution533ms
Transfer15 KB
Monthly Cost$7/mo
Google Tag Manager
Tag Manager
Costly
Execution286ms
Transfer147 KB
Unused42%
Monthly Cost$4/mo
Google Tag Manager
Tag Manager
Costly
Execution250ms
Transfer158 KB
Unused39%
Monthly Cost$3/mo
www.ornl.gov
Other
Costly
Execution231ms
Transfer1 KB
Monthly Cost$3/mo
Google Tag Manager
Tag Manager
Costly
Execution200ms
Transfer119 KB
Unused52%
Monthly Cost$3/mo
use.fontawesome.com
Other
Optional
Execution143ms
Transfer248 KB
Monthly Cost$2/mo
dap.digitalgov.gov
Other
Optional
Execution107ms
Transfer4 KB
Monthly Cost$1/mo
siteimproveanalytics.com
Other
Optional
Execution100ms
Transfer21 KB
Monthly Cost$1/mo
Google Tag Manager
Tag Manager
Optional
Execution88ms
Transfer147 KB
Unused72%
Monthly Cost$1/mo
www.ornl.gov
Other
Optional
Execution82ms
Transfer4 KB
Monthly Cost$1/mo
www.ornl.gov
Other
Optional
Execution61ms
Transfer35 KB
Monthly Cost$1/mo
These scripts may cost more than they're worth
Unattributable adds 692ms and costs ~$9/month
www.ornl.gov adds 533ms and costs ~$7/month
Google Tag Manager adds 286ms and costs ~$4/month
Google Tag Manager adds 250ms and costs ~$3/month
www.ornl.gov adds 231ms and costs ~$3/month
Google Tag Manager adds 200ms 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 692ms 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.ornl.gov takes 533ms 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 286ms 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 250ms 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.ornl.gov takes 231ms 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 200ms 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
52% 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
72% 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.