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https://svelte.dev

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
76
GRADE
C
FIX
3
REVIEW
3
PASS
6
INFO
2

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop
91
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
100
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
100
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

1.53 s

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

3.41 s

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

39 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.000

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

2.56 s

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

3.49 s

Page Load Progression

375 ms
750 ms
1.1 s
1.5 s
1.9 s
2.2 s
2.6 s
3.0 s
Checks
14
6 PASS 3 REVIEW 3 FIX
F
Page Weight Budget
Action
4.3 MB transferred, 72 requests
FIX
4.3 MB transferred, 72 requests
Critical::
Page weighs 5.6 MB (4.3 MB transferred)
Info::
72 HTTP requests
Info::
Estimated 0.89 g CO2 per page load
4.3 MB / 2.4 MB budget
4.3 MB transferred
72 requests
0.89 g CO2 per page load
Other 3.3 MiB 79%
Images 356.3 KiB 8%
Other 351.9 KiB 8%
JavaScript 105.7 KiB 2%
Fonts 69.2 KiB 2%
HTML 23.4 KiB 1%
CSS 22.5 KiB 1%
Other 3.6 KiB 0%
Other 656 B 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Over budget
D
Third-Party Impact
Action
79% third-party, 0 ms blocking
FIX
79% third-party, 0 ms blocking
Warning::
Third-party code accounts for 79% of page weight (3.3 MiB of 4.3 MiB)
Info::
Third-party blocking time is low (0 ms)
21%
79%
First-party Third-party
D
JS Execution Cost
Action
2290ms total JS execution
FIX
2290ms total JS execution
Warning::
Unattributable: 792ms CPU time
Warning::
https://svelte.dev/: 763ms CPU time
Warning::
https://svelte.dev/_app/immutable/chunks/DnTnPfQe....: 735ms CPU time
Info::
Third-party scripts: 792ms (35% of total)

Main Thread Breakdown

Other 43% Script Evaluation 24% Style & Layout 20% Rendering 9%
ScriptTotalScriptingParse/CompileParty
Unattributable792ms90ms0ms3rd
https://svelte.dev/763ms75ms10ms1st
https://svelte.dev/_app/immutable/chunks/DnTnPfQe.js735ms403ms1ms1st
B
Image Optimization
18 images, 0 KB saveable
REVIEW
18 images, 0 KB saveable
Info::
All images are well-optimized
18 images 356 KB
0 oversized -0 KB
6 legacy format
0 missing dimensions CLS risk
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

B
HTTP Caching
public, max-age=0, must-revalidate
REVIEW
public, max-age=0, must-revalidate
Info::
Cache-Control header is set
Got: public, max-age=0, must-revalidate
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present
Cache-Control

public, max-age=0, must-revalidate

DirectiveValueMeaning
public—Any cache may store this response
max-age0Cache for 0 seconds
must-revalidate—Must recheck with server after expiry
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
3 fonts (69 KB)
PASS
3 fonts (69 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

69 KB total

Render-blocking

0

of 3

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 1.0 s 2.0 s 3.0 s FCP 1.5 s LCP 3.4 shttps://svelte.dev/_app/immutable/assets/eb-garamond-latin-400-normal.DSJrtJSV.woff2eb-garamond-latin-400-n... https://svelte.dev/_app/immutable/assets/eb-garamond-latin-400-normal.DSJrtJSV.woff2 — 21.4 KiB — 0 ms — font-display: swaphttps://svelte.dev/_app/immutable/assets/dm-serif-display-latin-400-normal.C5_t9oOD.woff2dm-serif-display-latin-... https://svelte.dev/_app/immutable/assets/dm-serif-display-latin-400-normal.C5_t9oOD.woff2 — 24.3 KiB — 0 ms — font-display: swaphttps://svelte.dev/_app/immutable/assets/fira-sans-latin-400-normal.a0AnQzuD.woff2fira-sans-latin-400-nor... https://svelte.dev/_app/immutable/assets/fira-sans-latin-400-normal.a0AnQzuD.woff2 — 23.5 KiB — 0 ms — font-display: swap
eb-garamond-latin-400-n... woff2 swap
Size 21 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
dm-serif-display-latin-... woff2 swap
Size 24 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
fira-sans-latin-400-nor... woff2 swap
Size 23 KB
Load time 0 ms
Start 0 ms
Risk FOUT — 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+
JS Bundles
28 scripts, 0 KB unused
PASS
28 scripts, 0 KB unused
0 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://svelte.dev/_app/immutable/entry/start.Ddn2_gng.js0 KB—✓1st
https://svelte.dev/_app/immutable/chunks/BbUITsMw.js13 KB—✓1st
https://svelte.dev/_app/immutable/chunks/2d-wjCb2.js1 KB—✓1st
https://svelte.dev/_app/immutable/chunks/DnTnPfQe.js23 KB—✓1st
https://svelte.dev/_app/immutable/chunks/gDVcjQvr.js1 KB—✓1st
https://svelte.dev/_app/immutable/entry/app.BfHSeXOh.js3 KB—✓1st
https://svelte.dev/_app/immutable/chunks/Shm_I8ZE.js1 KB—✓1st
https://svelte.dev/_app/immutable/chunks/Dr15X4ZF.js0 KB—✓1st
https://svelte.dev/_app/immutable/chunks/cnniI1X3.js0 KB—✓1st
https://svelte.dev/_app/immutable/nodes/0.CPp9tl-V.js6 KB—✓1st
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
3 hints, 0 missing preconnects
PASS
3 hints, 0 missing preconnects
Info::
Page uses 3 resource hint(s)

Current Resource Hints

preconnect
—
preload
3
dns-prefetch
—
prefetch
—

3 resource hints configured

Network Waterfall
72 requests over 0ms
INFO

Performance analysis not available for this result.

Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
35% of JavaScript execution is third-party
First-party Third-party 792ms · 0KB · $11/mo
Unattributable
Other
Costly
Execution 792ms
Transfer 0 KB
Monthly Cost $11/mo

These scripts may cost more than they're worth

  • Unattributable adds 792ms and costs ~$11/month

Unattributable takes 792ms 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

How third-party costs are calculated

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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