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
41 images, 0 KB saveable
REVIEW
41 images, 0 KB saveable
Warning::
!
https://www.divephotoguide.com/images/features/l/1... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/files/uploaded_file... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/images/news/l/17763... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/images/features/l/1... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/files/uploaded_file... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/files/uploaded_file... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/images/features/l/1... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/files/uploaded_file... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/images/news/l/17742... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/images/travels/l/17... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/images/techniques/l... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/images/features/l/1... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.divephotoguide.com/files/uploaded_file... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
41images4.8 MB
0oversized-0 KB
37legacy format
13missing 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
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
6 fonts (242 KB)
PASS
6 fonts (242 KB)
Info::
i
6 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
6
242 KB total
Render-blocking
0
of 6
Dominant font-display
swap
Most common across fonts
Font loading timeline
TransferFOIT (block)FOUT (swap)
530dee22-e3c1-4e9f-bf62...woffswap
Size56 KB
Load time220 ms
Start1.6 s
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
558e1882-61fa-42c9-b946...woffswap
Size20 KB
Load time229 ms
Start1.6 s
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
7cc7234f-05ac-4109-8b8a...woffswap
Size25 KB
Load time272 ms
Start1.7 s
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
8e9ee02b-f337-4f13-ad6c...woffswap
Size67 KB
Load time272 ms
Start1.7 s
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
060031a3-ab11-4f91-9dd4...woffswap
Size36 KB
Load time289 ms
Start1.7 s
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
41c174b1-68c1-41b7-a19f...woffswap
Size38 KB
Load time298 ms
Start1.7 s
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 ~73 KB and ~146 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
112 requests over 3715ms
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-party3061ms · 654KB · $41/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
securepubads.g.doubleclick.net
securepubads.g.doubleclick.net
Other
1036ms
187 KB
55%
$14/mo
Costly
Unattributable
Unattributable
Other
521ms
0 KB
—
$7/mo
Costly
pagead2.googlesyndication.com
pagead2.googlesyndication.com
Other
441ms
0 KB
42%
$6/mo
Costly
www.divephotoguide.com
www.divephotoguide.com
Other
260ms
2 KB
—
$3/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
237ms
157 KB
42%
$3/mo
Costly
www.divephotoguide.com
www.divephotoguide.com
Other
227ms
56 KB
—
$3/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
108ms
117 KB
55%
$1/mo
Optional
Facebook Pixel
connect.facebook.net
Advertising
84ms
83 KB
65%
$1/mo
Optional
www.googletagservices.com
www.googletagservices.com
Other
77ms
34 KB
—
$1/mo
Optional
Google Analytics
ssl.google-analytics.com
Analytics
69ms
17 KB
—
$1/mo
Optional
securepubads.g.doubleclick.net
Other
Costly
Execution1036ms
Transfer187 KB
Unused55%
Monthly Cost$14/mo
Unattributable
Other
Costly
Execution521ms
Transfer0 KB
Monthly Cost$7/mo
pagead2.googlesyndication.com
Other
Costly
Execution441ms
Transfer0 KB
Unused42%
Monthly Cost$6/mo
www.divephotoguide.com
Other
Costly
Execution260ms
Transfer2 KB
Monthly Cost$3/mo
Google Tag Manager
Tag Manager
Costly
Execution237ms
Transfer157 KB
Unused42%
Monthly Cost$3/mo
www.divephotoguide.com
Other
Costly
Execution227ms
Transfer56 KB
Monthly Cost$3/mo
Google Tag Manager
Tag Manager
Optional
Execution108ms
Transfer117 KB
Unused55%
Monthly Cost$1/mo
Facebook Pixel
Advertising
Optional
Execution84ms
Transfer83 KB
Unused65%
Monthly Cost$1/mo
www.googletagservices.com
Other
Optional
Execution77ms
Transfer34 KB
Monthly Cost$1/mo
Google Analytics
Analytics
Optional
Execution69ms
Transfer17 KB
Monthly Cost$1/mo
These scripts may cost more than they're worth
securepubads.g.doubleclick.net adds 1036ms and costs ~$14/month
Unattributable adds 521ms and costs ~$7/month
pagead2.googlesyndication.com adds 441ms and costs ~$6/month
www.divephotoguide.com adds 260ms and costs ~$3/month
Google Tag Manager adds 237ms and costs ~$3/month
www.divephotoguide.com adds 227ms 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
securepubads.g.doubleclick.net takes 1036ms 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
55% 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
Unattributable takes 521ms 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
pagead2.googlesyndication.com takes 441ms 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.divephotoguide.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
Google Tag Manager takes 237ms 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.divephotoguide.com takes 227ms 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
55% 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
65% of Facebook Pixel'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.