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
28 images, 0 KB saveable
REVIEW
28 images, 0 KB saveable
Warning::
!
https://www.uam.es/uam/media/imgm/1607029033883/la... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/img/1606995215633/por... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/imgm/1606903067572/fo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/img/1606848842439/hr-... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/img/1606893866850/uam... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/img/1606928370518/inf... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/img/1606957595533/par... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/imgl/1607033349710/20... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/imgm/1606859313941/ba... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/img/1606848841888/uni... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/imgm/1606937915229/im... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/img/1606848842193/fue... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.uam.es/uam/media/img/1606848842005/san... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
28images2.4 MB
0oversized-0 KB
28legacy 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
4 fonts (107 KB)
PASS
4 fonts (107 KB)
Info::
i
4 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
4
107 KB total
Render-blocking
0
of 4
Dominant font-display
swap
Most common across fonts
Font loading timeline
TransferFOIT (block)FOUT (swap)
KFO7CnqEu92Fr1ME7kSn66a...woff2swap
Size37 KB
Load time12 ms
Start2.2 s
RiskFOUT — text flashes from fallback to web font
uam-icons.woff2woff2swap
Size8 KB
Load time239 ms
Start2.2 s
RiskFOUT — text flashes from fallback to web font
nuFvD-vYSZviVYUb_rj3ij_...woff2swap
Size21 KB
Load time15 ms
Start2.2 s
RiskFOUT — text flashes from fallback to web font
KFO5CnqEu92Fr1Mu53ZEC9_...woff2swap
Size41 KB
Load time16 ms
Start2.2 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)
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
54 requests over 3858ms
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-party5215ms · 1468KB · €57/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
www.uam.es
www.uam.es
Other
1623ms
78 KB
—
€18/mo
Costly
Unattributable
Unattributable
Other
1194ms
0 KB
—
€13/mo
Costly
www.uam.es
www.uam.es
Other
1125ms
477 KB
67%
€12/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
615ms
177 KB
39%
€7/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
419ms
139 KB
51%
€5/mo
Costly
Google Tag Manager
www.googletagmanager.com
Tag Manager
134ms
143 KB
40%
€1/mo
Optional
www.uam.es
www.uam.es
Other
54ms
2 KB
—
€1/mo
Optional
www.uam.es
www.uam.es
Other
51ms
453 KB
—
€1/mo
Optional
www.uam.es
Other
Costly
Execution1623ms
Transfer78 KB
Monthly Cost€18/mo
Unattributable
Other
Costly
Execution1194ms
Transfer0 KB
Monthly Cost€13/mo
www.uam.es
Other
Costly
Execution1125ms
Transfer477 KB
Unused67%
Monthly Cost€12/mo
Google Tag Manager
Tag Manager
Costly
Execution615ms
Transfer177 KB
Unused39%
Monthly Cost€7/mo
Google Tag Manager
Tag Manager
Costly
Execution419ms
Transfer139 KB
Unused51%
Monthly Cost€5/mo
Google Tag Manager
Tag Manager
Optional
Execution134ms
Transfer143 KB
Unused40%
Monthly Cost€1/mo
www.uam.es
Other
Optional
Execution54ms
Transfer2 KB
Monthly Cost€1/mo
www.uam.es
Other
Optional
Execution51ms
Transfer453 KB
Monthly Cost€1/mo
These scripts may cost more than they're worth
www.uam.es adds 1623ms and costs ~€18/month
Unattributable adds 1194ms and costs ~€13/month
www.uam.es adds 1125ms and costs ~€12/month
Google Tag Manager adds 615ms and costs ~€7/month
Google Tag Manager adds 419ms and costs ~€5/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
www.uam.es takes 1623ms 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
Unattributable takes 1194ms 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.uam.es takes 1125ms 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
67% of www.uam.es'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 615ms 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 419ms 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
51% 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.