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Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
91
GRADE
A
FIX
2
REVIEW
2
PASS
10
INFO
2

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

Mobile Desktop
72
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
97
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.

3.16 s

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

4.13 s

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

88 ms

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

0.178

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

3.23 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.

4.14 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
10 PASS 2 REVIEW 2 FIX
D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (457.2 KiB of 457.3 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
No Cache-Control header found
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
JS Execution Cost
Action
1106ms total JS execution
REVIEW
1106ms total JS execution
Warning::
Unattributable: 378ms CPU time
Warning::
https://nixos.org/_astro/Asciinema.astro_astro_typ...: 339ms CPU time
Warning::
https://nixos.org/: 336ms CPU time
Info::
https://nixos.org/_astro/Layout.astro_astro_type_s...: 53ms CPU time
Warning::
Third-party scripts: 1106ms (100% of total)

Main Thread Breakdown

Other 35% Script Evaluation 30% Style & Layout 26% Rendering 5% Parse HTML & CSS 4%
ScriptTotalScriptingParse/CompileParty
Unattributable378ms105ms0ms3rd
https://nixos.org/_astro/Asciinema.astro_astro_type_script_index_0_lang.9jNJCMF_.js339ms182ms1ms3rd
https://nixos.org/336ms12ms1ms3rd
https://nixos.org/_astro/Layout.astro_astro_type_script_index_0_lang.Cg311B8L.js53ms41ms0ms3rd
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Page Weight Budget
457 KB transferred, 25 requests
PASS
457 KB transferred, 25 requests
Info::
Page weighs 827 KB (457 KB transferred)
Info::
25 HTTP requests
Info::
Estimated 0.09 g CO2 per page load
457 KB / 2.4 MB budget
457 KB transferred
25 requests
0.09 g CO2 per page load
Other 159.3 KiB 35%
Fonts 141.9 KiB 31%
JavaScript 79.0 KiB 17%
CSS 54.3 KiB 12%
HTML 12.0 KiB 3%
Other 8.0 KiB 2%
Images 2.2 KiB 0%
Other 640 B 0%
0 2.4 MB 4.9 MB
Under budget
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
Image Optimization
4 images, 0 KB saveable
PASS
4 images, 0 KB saveable
Info::
All images are well-optimized
4 images 2 KB
0 oversized -0 KB
2 legacy format
0 missing dimensions CLS risk
A+
Font Loading
4 fonts (142 KB)
PASS
4 fonts (142 KB)
Info::
4 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

4

142 KB total

Render-blocking

0

of 4

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 4.0 s FCP 3.2 s LCP 4.1 shttps://nixos.org/_astro/fira-code-latin-wght-normal.CHoedHDv.woff2fira-code-latin-wght-no... https://nixos.org/_astro/fira-code-latin-wght-normal.CHoedHDv.woff2 — 35.5 KiB — 0 ms — font-display: swaphttps://nixos.org/fonts/route159/Route159-Heavy.woffRoute159-Heavy.woff https://nixos.org/fonts/route159/Route159-Heavy.woff — 23.8 KiB — 0 ms — font-display: swaphttps://nixos.org/fonts/route159/Route159-Bold.woffRoute159-Bold.woff https://nixos.org/fonts/route159/Route159-Bold.woff — 24.3 KiB — 0 ms — font-display: swaphttps://nixos.org/_astro/roboto-flex-latin-wdth-normal.BPCCEOJP.woff2roboto-flex-latin-wdth-... https://nixos.org/_astro/roboto-flex-latin-wdth-normal.BPCCEOJP.woff2 — 58.3 KiB — 0 ms — font-display: swap
fira-code-latin-wght-no... woff2 swap
Size 36 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Route159-Heavy.woff woff swap
Size 24 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
Route159-Bold.woff woff swap
Size 24 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
roboto-flex-latin-wdth-... woff2 swap
Size 58 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 ~14 KB and ~28 ms

A+
JS Bundles
2 scripts, 0 KB unused
PASS
2 scripts, 0 KB unused
0 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://nixos.org/_astro/Asciinema.astro_astro_type_script_index_0_lang.9jNJCMF_.js61 KB—✓3rd
https://nixos.org/_astro/Layout.astro_astro_type_script_index_0_lang.Cg311B8L.js18 KB—✓3rd
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
25 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
100% of JavaScript execution is third-party
First-party Third-party 1106ms · 91KB · €12/mo
Unattributable
Other
Costly
Execution 378ms
Transfer 0 KB
Monthly Cost €4/mo
nixos.org
Other
Costly
Execution 339ms
Transfer 61 KB
Monthly Cost €4/mo
nixos.org
Other
Costly
Execution 336ms
Transfer 12 KB
Monthly Cost €4/mo
nixos.org
Other
Optional
Execution 53ms
Transfer 18 KB
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • Unattributable adds 378ms and costs ~€4/month
  • nixos.org adds 339ms and costs ~€4/month
  • nixos.org adds 336ms and costs ~€4/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 378ms 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

nixos.org takes 339ms 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

nixos.org takes 336ms 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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