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
73 images, 0 KB saveable
REVIEW
73 images, 0 KB saveable
Warning::
!
https://www.enel.it/etc.clientlibs/enel-it/clientl... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.enel.it/content/dam/enel-common-lib/im... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.enel.it/content/dam/asset/immagini/ass... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.enel.it/content/dam/asset/immagini/ene... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.enel.it/content/dam/enel-common-lib/im... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.enel.it/content/dam/asset/immagini/ene... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://www.enel.it/content/dam/asset/immagini/ass... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
73images1.1 MB
0oversized-0 KB
58legacy format
7missing 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
B
HTTP/3 (QUIC)
HTTP/3 not advertised
REVIEW
HTTP/3 not advertised
Info::
i
HTTP/3 (QUIC) is not advertised
HTTP/3 isn't advertised via Alt-Svc and the worker didn't negotiate h3. HTTP/3 reduces handshake latency (1-RTT instead of 2-3 RTTs) and is more resilient on lossy connections. Most modern CDNs (Cloudflare, Fastly, AWS CloudFront, Google Cloud CDN) support HTTP/3 with a single config switch -- consider enabling for mobile-heavy workloads.
C
Compression Algorithm
Action
Main response served uncompressed
REVIEW
Main response served uncompressed
Info::
i
Main HTML response has no Content-Encoding (uncompressed)
The main HTML document is served without compression. The Text Compression section above lists the broader picture; for the main response specifically, even gzip would shave ~70-80% off most text payloads.
B
Main HTML Cache-Control
No Cache-Control header on main HTML response
REVIEW
No Cache-Control header on main HTML response
Info::
i
Main HTML response has no Cache-Control header
Without an explicit Cache-Control, browsers fall back to heuristic caching (~10% of Last-Modified age). Set `Cache-Control: no-cache` or `max-age=300` for HTML to control freshness explicitly -- prevents stale auth state and SPA shell drift.
B
Server-Timing Observability
No Server-Timing header found
REVIEW
No Server-Timing header found
Info::
i
No Server-Timing header found
Server-Timing exposes backend timing breakdowns to browser DevTools (e.g., `db: 45ms; render: 120ms; cache: 2ms`). Useful for diagnosing slow pages without backend log access. Most modern frameworks (Next.js, Cloudflare Workers, Fastly) emit it automatically; absence on a managed platform usually means telemetry headers are stripped at the edge.
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
11 fonts (372 KB)
PASS
11 fonts (372 KB)
Info::
i
11 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
11
372 KB total
Render-blocking
0
of 11
Dominant font-display
swap
Most common across fonts
Font loading timeline
TransferFOIT (block)FOUT (swap)
RoobertENEL-Light.woff2woff2swap
Size43 KB
Load time63 ms
Start303 ms
RiskFOUT — text flashes from fallback to web font
roobertenel-regular-web...woff2swap
Size21 KB
Load time68 ms
Start304 ms
RiskFOUT — text flashes from fallback to web font
roobertenel-bold-webfon...woff2swap
Size21 KB
Load time70 ms
Start305 ms
RiskFOUT — text flashes from fallback to web font
RoobertENEL-Black.woff2woff2swap
Size45 KB
Load time72 ms
Start305 ms
RiskFOUT — text flashes from fallback to web font
font-woff;charset=utf-8...woffswap
Size2 KB
Load time227 ms
Start763 ms
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
roobertenel-regular-web...woff2swap
Size21 KB
Load time36 ms
Start906 ms
RiskFOUT — text flashes from fallback to web font
roobertenel-bold-webfon...woff2swap
Size21 KB
Load time38 ms
Start906 ms
RiskFOUT — text flashes from fallback to web font
RoobertENEL-Light.woff2woff2swap
Size43 KB
Load time89 ms
Start1.2 s
RiskFOUT — text flashes from fallback to web font
KFO7CnqEu92Fr1ME7kSn66a...woff2swap
Size34 KB
Load time76 ms
Start4.3 s
RiskFOUT — text flashes from fallback to web font
getttfswap
Size60 KB
Load time11 ms
Start5.8 s
RiskFOUT — text flashes from fallback to web font
Convert to woff2 for ~30% smaller file size
getttfswap
Size60 KB
Load time11 ms
Start5.8 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 ~36 KB and ~72 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
4 hints, 0 missing preconnects
PASS
4 hints, 0 missing preconnects
Info::
✓
Page uses 4 resource hint(s)
Current Resource Hints
preconnect—
preload
4
dns-prefetch—
prefetch—
4 resource hints configured
A+
LCP Image Preload
LCP preload audit not available
PASS
LCP preload audit not available
Info::
✓
LCP image preload audit not available for this scan
A+
Server Response Intelligence
1 server-response signal(s) detected
PASS
1 server-response signal(s) detected
Info::
i
No `ETag` or `Last-Modified` -- conditional GET not supported
Without either header, browsers can't issue conditional GETs and refresh always re-downloads the full response body even when nothing changed. Add `ETag: "<hash>"` (or `Last-Modified: <date>`) on cacheable responses; the server returns 304 Not Modified when the client's cached copy is still valid, saving bandwidth.
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
A
JavaScript Blocking
1 JS blocking issue(s) detected
PASS
1 JS blocking issue(s) detected
Warning::
!
Total JS execution time is 25.2 s -- over the 3.5s budget
Total JavaScript execution (parse + compile + run) across all scripts exceeds 3.5 seconds. On low-end devices that becomes 7-15+ seconds and shows up directly in TBT and INP. Reduce by: tree-shaking unused dependencies, code-splitting (dynamic `import()`), removing or deferring third-party tracking, and replacing heavy frameworks where they're not needed.
Each `<link rel="stylesheet">` without a non-blocking `media` attribute holds up the first paint. Browsers download all of them before painting any content. Consolidate into 1-2 critical-path stylesheets; defer non-critical CSS via `<link rel="stylesheet" media="print" onload="this.media='all'">` or via the loadCSS pattern; inline above-the-fold CSS in `<style>` to short-circuit the request entirely.
Network Waterfall
230 requests over 9526ms
INFO
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
88%of JavaScript execution is third-party
First-party Third-party22300ms · 1508KB · €242/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
www.enel.it
www.enel.it
Other
4524ms
45 KB
49%
€49/mo
Costly
www.enel.it
www.enel.it
Other
3916ms
24 KB
84%
€43/mo
Costly
www.enel.it
www.enel.it
Other
3090ms
97 KB
34%
€34/mo
Costly
www.gstatic.com
www.gstatic.com
Other
2956ms
0 KB
50%
€32/mo
Costly
www.enel.it
www.enel.it
Other
2096ms
124 KB
—
€23/mo
Costly
www.enel.it
www.enel.it
Other
2052ms
233 KB
—
€22/mo
Costly
www.enel.it
www.enel.it
Other
624ms
151 KB
47%
€7/mo
Costly
assets.adobedtm.com
assets.adobedtm.com
Other
482ms
97 KB
35%
€5/mo
Costly
www.enel.it
www.enel.it
Other
311ms
14 KB
—
€3/mo
Costly
consent.trustarc.com
consent.trustarc.com
Other
250ms
14 KB
—
€3/mo
Costly
www.enel.it
www.enel.it
Other
229ms
3 KB
—
€2/mo
Costly
www.enel.it
www.enel.it
Other
164ms
0 KB
—
€2/mo
Optional
www.enel.it
www.enel.it
Other
162ms
43 KB
67%
€2/mo
Optional
www.enel.it
www.enel.it
Other
153ms
1 KB
—
€2/mo
Optional
www.enel.it
www.enel.it
Other
139ms
2 KB
—
€2/mo
Optional
www.enel.it
www.enel.it
Other
128ms
206 KB
—
€1/mo
Optional
www.enel.it
www.enel.it
Other
118ms
157 KB
46%
€1/mo
Optional
consent.trustarc.com
consent.trustarc.com
Other
112ms
31 KB
70%
€1/mo
Optional
www.enel.it
www.enel.it
Other
109ms
5 KB
—
€1/mo
Optional
www.enel.it
www.enel.it
Other
108ms
42 KB
62%
€1/mo
Optional
www.enel.it
www.enel.it
Other
105ms
145 KB
50%
€1/mo
Optional
www.enel.it
www.enel.it
Other
104ms
1 KB
—
€1/mo
Optional
www.enel.it
www.enel.it
Other
78ms
1 KB
—
€1/mo
Optional
assets.adobedtm.com
assets.adobedtm.com
Other
69ms
1 KB
—
€1/mo
Optional
www.enel.it
www.enel.it
Other
61ms
19 KB
—
€1/mo
Optional
www.enel.it
www.enel.it
Other
54ms
5 KB
—
€1/mo
Optional
www.enel.it
www.enel.it
Other
52ms
45 KB
76%
€1/mo
Optional
www.enel.it
www.enel.it
Other
51ms
3 KB
—
€1/mo
Optional
www.enel.it
Other
Costly
Execution4524ms
Transfer45 KB
Unused49%
Monthly Cost€49/mo
www.enel.it
Other
Costly
Execution3916ms
Transfer24 KB
Unused84%
Monthly Cost€43/mo
www.enel.it
Other
Costly
Execution3090ms
Transfer97 KB
Unused34%
Monthly Cost€34/mo
www.gstatic.com
Other
Costly
Execution2956ms
Transfer0 KB
Unused50%
Monthly Cost€32/mo
www.enel.it
Other
Costly
Execution2096ms
Transfer124 KB
Monthly Cost€23/mo
www.enel.it
Other
Costly
Execution2052ms
Transfer233 KB
Monthly Cost€22/mo
www.enel.it
Other
Costly
Execution624ms
Transfer151 KB
Unused47%
Monthly Cost€7/mo
assets.adobedtm.com
Other
Costly
Execution482ms
Transfer97 KB
Unused35%
Monthly Cost€5/mo
www.enel.it
Other
Costly
Execution311ms
Transfer14 KB
Monthly Cost€3/mo
consent.trustarc.com
Other
Costly
Execution250ms
Transfer14 KB
Monthly Cost€3/mo
www.enel.it
Other
Costly
Execution229ms
Transfer3 KB
Monthly Cost€2/mo
www.enel.it
Other
Optional
Execution164ms
Transfer0 KB
Monthly Cost€2/mo
www.enel.it
Other
Optional
Execution162ms
Transfer43 KB
Unused67%
Monthly Cost€2/mo
www.enel.it
Other
Optional
Execution153ms
Transfer1 KB
Monthly Cost€2/mo
www.enel.it
Other
Optional
Execution139ms
Transfer2 KB
Monthly Cost€2/mo
www.enel.it
Other
Optional
Execution128ms
Transfer206 KB
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution118ms
Transfer157 KB
Unused46%
Monthly Cost€1/mo
consent.trustarc.com
Other
Optional
Execution112ms
Transfer31 KB
Unused70%
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution109ms
Transfer5 KB
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution108ms
Transfer42 KB
Unused62%
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution105ms
Transfer145 KB
Unused50%
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution104ms
Transfer1 KB
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution78ms
Transfer1 KB
Monthly Cost€1/mo
assets.adobedtm.com
Other
Optional
Execution69ms
Transfer1 KB
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution61ms
Transfer19 KB
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution54ms
Transfer5 KB
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution52ms
Transfer45 KB
Unused76%
Monthly Cost€1/mo
www.enel.it
Other
Optional
Execution51ms
Transfer3 KB
Monthly Cost€1/mo
These scripts may cost more than they're worth
www.enel.it adds 4524ms and costs ~€49/month
www.enel.it adds 3916ms and costs ~€43/month
www.enel.it adds 3090ms and costs ~€34/month
www.gstatic.com adds 2956ms and costs ~€32/month
www.enel.it adds 2096ms and costs ~€23/month
www.enel.it adds 2052ms and costs ~€22/month
www.enel.it adds 624ms and costs ~€7/month
assets.adobedtm.com adds 482ms and costs ~€5/month
www.enel.it adds 311ms and costs ~€3/month
consent.trustarc.com adds 250ms and costs ~€3/month
www.enel.it adds 229ms and costs ~€2/month
88% 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.enel.it takes 4524ms 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.enel.it takes 3916ms 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
84% of www.enel.it'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
www.enel.it takes 3090ms 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.gstatic.com takes 2956ms 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.enel.it takes 2096ms 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.enel.it takes 2052ms 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.enel.it takes 624ms 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
assets.adobedtm.com takes 482ms 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.enel.it takes 311ms 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
consent.trustarc.com 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.enel.it takes 229ms 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.enel.it'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
70% of consent.trustarc.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
62% of www.enel.it'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
50% of www.enel.it'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
76% of www.enel.it'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.