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
Page Weight Budget
Action
2.0 MB transferred, 101 requests
REVIEW
2.0 MB transferred, 101 requests
Info::
i
Page weighs 4.9 MB (2.0 MB transferred)
Warning::
!
JavaScript is 951 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 951 KB
Info::
i
Fonts are 218 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 218 KB
Warning::
!
101 HTTP requests — consider bundling or reducing
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Info::
i
Estimated 0.43 g CO2 per page load
2.0 MBtransferred
101 requests
0.43 g CO2 per page load
JavaScript951.0 KiB46%
Images760.9 KiB37%
Fonts218.2 KiB10%
CSS105.5 KiB5%
HTML40.5 KiB2%
Other2.6 KiB0%
Other1.0 KiB0%
02.4 MB4.9 MB
Approaching limit
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Why this matters
JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.
Source: web.dev
Subset fonts to include only used characters, or switch to system font stacks.
Why this matters
Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).
Source: web.dev font loading
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Why this matters
High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.
Source: web.dev
C
Image Optimization
Action
53 images, 0 KB saveable
REVIEW
53 images, 0 KB saveable
Warning::
!
https://cdn.vocabulary.com/images/home/awards/tech... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://cdn.vocabulary.com/images/home/looking-for... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://cdn.vocabulary.com/images/footer/logo-voca... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://cdn.vocabulary.com/images/home/awards/the-... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://cdn.vocabulary.com/images/home/awards/read... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://cdn.vocabulary.com/images/footer/logo-ixl-... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://cdn.vocabulary.com/images/home/looking-for... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
!
https://cdn.vocabulary.com/images/home/awards/tech... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
53images761 KB
0oversized-0 KB
53legacy format
8missing 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
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 (218 KB)
PASS
4 fonts (218 KB)
Info::
i
4 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
4
218 KB total
Render-blocking
0
of 4
Dominant font-display
swap
Most common across fonts
Font loading timeline
TransferFOIT (block)FOUT (swap)
memvYaGs126MiZpBA-UvWbX...woff2swap
Size42 KB
Load time74 ms
Start993 ms
RiskFOUT — text flashes from fallback to web font
memtYaGs126MiZpBA-UFUIc...woff2swap
Size44 KB
Load time76 ms
Start993 ms
RiskFOUT — text flashes from fallback to web font
u-4c0qyriQwlOrhSvowK_l5...woff2swap
Size98 KB
Load time48 ms
Start1.3 s
RiskFOUT — text flashes from fallback to web font
KFO7CnqEu92Fr1ME7kSn66a...woff2swap
Size34 KB
Load time66 ms
Start1.6 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
2 hints, 0 missing preconnects
PASS
2 hints, 0 missing preconnects
Info::
✓
Page uses 2 resource hint(s)
Current Resource Hints
preconnect
2
preload—
dns-prefetch—
prefetch—
2 resource hints configured
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+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS
Green Hosting
This site is hosted on green energy infrastructure
Provider: Cloudflare
Network Waterfall
101 requests over 1946ms
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-party2126ms · 48KB · €23/mo
Script
Category
Execution
Transfer
Unused
Monthly Cost
Verdict
Unattributable
Unattributable
Other
666ms
0 KB
—
€7/mo
Costly
www.gstatic.com
www.gstatic.com
Other
658ms
0 KB
49%
€7/mo
Costly
www.vocabulary.com
www.vocabulary.com
Other
575ms
13 KB
—
€6/mo
Costly
cdn.vocabulary.com
cdn.vocabulary.com
Other
121ms
31 KB
—
€1/mo
Optional
cdn.vocabulary.com
cdn.vocabulary.com
Other
106ms
4 KB
—
€1/mo
Optional
Unattributable
Other
Costly
Execution666ms
Transfer0 KB
Monthly Cost€7/mo
www.gstatic.com
Other
Costly
Execution658ms
Transfer0 KB
Unused49%
Monthly Cost€7/mo
www.vocabulary.com
Other
Costly
Execution575ms
Transfer13 KB
Monthly Cost€6/mo
cdn.vocabulary.com
Other
Optional
Execution121ms
Transfer31 KB
Monthly Cost€1/mo
cdn.vocabulary.com
Other
Optional
Execution106ms
Transfer4 KB
Monthly Cost€1/mo
These scripts may cost more than they're worth
Unattributable adds 666ms and costs ~€7/month
www.gstatic.com adds 658ms and costs ~€7/month
www.vocabulary.com adds 575ms and costs ~€6/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 666ms 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 658ms 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.vocabulary.com takes 575ms 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.