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https://dart.dev

Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
86
GRADE
B
FIX
1
REVIEW
5
PASS
8
INFO
2

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

Mobile Desktop
95
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
96
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
96
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
92
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.

1.77 s

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

2.25 s

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

191 ms

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

0.004

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

1.77 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.

6.96 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
16
8 PASS 5 REVIEW 1 FIX
D
Third-Party Impact
Action
72% third-party, 0 ms blocking
FIX
72% third-party, 0 ms blocking
Warning::
Third-party code accounts for 72% of page weight (813.0 KiB of 1.1 MiB)
Info::
Third-party blocking time is low (0 ms)
28%
72%
First-party Third-party
B
Page Weight Budget
1.1 MB transferred, 43 requests
REVIEW
1.1 MB transferred, 43 requests
Info::
Page weighs 2.5 MB (1.1 MB transferred)
Info::
Fonts are 497 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 497 KB
Info::
43 HTTP requests
Info::
Estimated 0.23 g CO2 per page load
1.1 MB / 2.4 MB budget
1.1 MB transferred
43 requests
0.23 g CO2 per page load
Fonts 496.8 KiB 44%
JavaScript 313.3 KiB 28%
Other 165.6 KiB 15%
Images 67.6 KiB 6%
Other 60.1 KiB 5%
CSS 19.9 KiB 2%
HTML 11.9 KiB 1%
Other 460 B 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Under budget

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

C
Image Optimization
Action
9 images, 0 KB saveable
REVIEW
9 images, 0 KB saveable
Warning::
https://dart.dev/assets/img/logo/dart-192.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dart.dev/assets/dash/svg/1-1-async-await.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dart.dev/assets/dash/svg/2-1-hot-reload-it... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dart.dev/assets/img/logo/logo-white-text.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dart.dev/assets/dash/2x/supported-by-googl... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dart.dev/assets/dash/svg/3-1-aot-compile.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
9 images 68 KB
0 oversized -0 KB
9 legacy format
6 missing dimensions CLS 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

C
JS Execution Cost
Action
1300ms total JS execution
REVIEW
1300ms total JS execution
Warning::
https://dart.dev/: 461ms CPU time
Warning::
Unattributable: 297ms CPU time
Info::
https://www.googletagmanager.com/gtag/js?id=G-X5H2...: 188ms CPU time
Info::
https://dart.dev/main.client.mjs: 165ms CPU time
Info::
https://www.google-analytics.com/analytics.js: 96ms CPU time
Warning::
Third-party scripts: 674ms (52% of total)

Main Thread Breakdown

Script Evaluation 34% Other 27% Style & Layout 26% Script Parsing & Compilation 6% Parse HTML & CSS 4% Rendering 3%
ScriptTotalScriptingParse/CompileParty
https://dart.dev/461ms15ms2ms1st
Unattributable297ms11ms0ms3rd
https://www.googletagmanager.com/gtag/js?id=G-X5H2ZXSYH5&cx=c&_slc=1188ms152ms35ms3rd
https://dart.dev/main.client.mjs165ms137ms0ms1st
https://www.google-analytics.com/analytics.js96ms86ms5ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-5VSZM5J93ms59ms31ms3rd
B
JS Bundles
6 scripts, 134 KB unused
REVIEW
6 scripts, 134 KB unused
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-5VS...: 73 KB unused (55%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-X5H2...: 62 KB unused (41%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 134 KB
134 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtm.js?id=GTM-5VSZM5J132 KB73 KB (55%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-X5H2ZXSYH5&cx=c&_slc=1150 KB62 KB (41%)✓3rd
https://cdn.jsdelivr.net/npm/@justinribeiro/lite-youtube@1.8.2/lite-youtube.js4 KB—✓3rd
https://dart.dev/main.client.dart.js1 KB—✓1st
https://www.google-analytics.com/analytics.js21 KB—✓3rd
https://dart.dev/main.client.mjs5 KB—✓1st

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

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
3 fonts (497 KB)
PASS
3 fonts (497 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

497 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 500 ms 1.0 s 1.5 s 2.0 s FCP 1.8 s LCP 2.3 shttps://fonts.gstatic.com/s/googlesans/v67/4UasrENHsxJlGDuGo1OIlJfC6l_24rlCK1Yo_Iqcsih3SAyH6cAwhX9RPjIUvbQoi-E.woff24UasrENHsxJlGDuGo1OIlJf... https://fonts.gstatic.com/s/googlesans/v67/4UasrENHsxJlGDuGo1OIlJfC6l_24rlCK1Yo_Iqcsih3SAyH6cAwhX9RPjIUvbQoi-E.woff2 — 35.3 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/materialsymbolsoutlined/v323/kJF4BvYX7BgnkSrUwT8OhrdQw4oELdPIeeII9v6oDMzBwG-RpA6RzaxHMPdY40KH8nGzv3fzfVJU22ZZLsYEpzC_1ver5Y0J1Llf.woff2kJF4BvYX7BgnkSrUwT8Ohrd... https://fonts.gstatic.com/s/materialsymbolsoutlined/v323/kJF4BvYX7BgnkSrUwT8OhrdQw4oELdPIeeII9v6oDMzBwG-RpA6RzaxHMPdY40KH8nGzv3fzfVJU22ZZLsYEpzC_1ver5Y0J1Llf.woff2 — 439.8 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/googlesanstext/v25/5aUu9-KzpRiLCAt4Unrc-xIKmCU5qEp2i0VBuxM.woff25aUu9-KzpRiLCAt4Unrc-xI... https://fonts.gstatic.com/s/googlesanstext/v25/5aUu9-KzpRiLCAt4Unrc-xIKmCU5qEp2i0VBuxM.woff2 — 21.6 KiB — 0 ms — font-display: swap
4UasrENHsxJlGDuGo1OIlJf... woff2 swap
Size 35 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
kJF4BvYX7BgnkSrUwT8Ohrd... woff2 swap
Size 440 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
5aUu9-KzpRiLCAt4Unrc-xI... woff2 swap
Size 22 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)

Fixing the unchecked items could save ~220 KB and ~440 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
6 hints, 0 missing preconnects
PASS
6 hints, 0 missing preconnects
Info::
Page uses 6 resource hint(s)

Current Resource Hints

preconnect
2
preload
—
dns-prefetch
—
prefetch
4

6 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+
HTTP Caching
max-age=3600 (1 hour)
PASS
max-age=3600 (1 hour)
Info::
Cache-Control header is set
Got: max-age=3600
Info::
Effective TTL: 1 hour (max-age=3600)
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present
Cache-Control

max-age=3600

DirectiveValueMeaning
max-age3600Cache for 1 hour
Effective TTL: 3600 seconds
Network Waterfall
43 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
52% of JavaScript execution is third-party
First-party Third-party 674ms · 303KB · €7/mo
Unattributable
Other
Costly
Execution 297ms
Transfer 0 KB
Monthly Cost €3/mo
Google Tag Manager
Tag Manager
Optional
Execution 188ms
Transfer 150 KB
Unused 41%
Monthly Cost €2/mo
Google Analytics
Analytics
Optional
Execution 96ms
Transfer 21 KB
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 93ms
Transfer 132 KB
Unused 55%
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • Unattributable adds 297ms and costs ~€3/month

52% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

Learn more ▾

Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

Unattributable takes 297ms 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

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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