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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
80
GRADE
B
FIX
2
REVIEW
2
PASS
8
INFO
2

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

Mobile Desktop
98
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
91
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.
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.

522 ms

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

1.16 s

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

0 ms

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

0.001

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

522 ms

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

1.19 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
8 PASS 2 REVIEW 2 FIX
F
Page Weight Budget
Action
4.6 MB transferred, 59 requests
FIX
4.6 MB transferred, 59 requests
Critical::
Page weighs 8.0 MB (4.6 MB transferred)
Info::
Fonts are 2.0 MB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 2.0 MB
Warning::
Images are 1.5 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 1.5 MB
Warning::
JavaScript is 853 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 853 KB
Info::
59 HTTP requests
Info::
Estimated 0.97 g CO2 per page load
4.6 MB / 2.4 MB budget
4.6 MB transferred
59 requests
0.97 g CO2 per page load
Fonts 2.0 MiB 44%
Images 1.5 MiB 32%
JavaScript 853.5 KiB 18%
CSS 139.9 KiB 3%
HTML 88.2 KiB 2%
Other 19.0 KiB 0%
Other 18.2 KiB 0%
Other 3.1 KiB 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Over 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

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Why this matters

Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.

Source: web.dev

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

D
Third-Party Impact
Action
70% third-party, 0 ms blocking
FIX
70% third-party, 0 ms blocking
Warning::
Third-party code accounts for 70% of page weight (3.2 MiB of 4.6 MiB)
Info::
Third-party blocking time is low (0 ms)
30%
70%
First-party Third-party
C
Image Optimization
Action
23 images, 0 KB saveable
REVIEW
23 images, 0 KB saveable
Warning::
https://www.julialang.org/assets/infra/juliacon_lo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.julialang.org/assets/infra/waves.webp is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
23 images 1.5 MB
0 oversized -0 KB
20 legacy format
2 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

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+
JS Execution Cost
421ms total JS execution
PASS
421ms total JS execution
Warning::
https://www.julialang.org/: 306ms CPU time
Info::
Unattributable: 115ms CPU time
Info::
Third-party scripts: 115ms (27% of total)

Main Thread Breakdown

Style & Layout 48% Other 30% Script Evaluation 11% Rendering 8%
ScriptTotalScriptingParse/CompileParty
https://www.julialang.org/306ms4ms0ms1st
Unattributable115ms1ms0ms3rd
A+
Font Loading
4 fonts (2066 KB)
PASS
4 fonts (2066 KB)
Info::
4 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

4

2066 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 500 ms 1.0 s FCP 522 ms LCP 1.2 shttps://cdn.jsdelivr.net/gh/cormullion/juliamono-webfonts/JuliaMono-Regular.woff2JuliaMono-Regular.woff2 https://cdn.jsdelivr.net/gh/cormullion/juliamono-webfonts/JuliaMono-Regular.woff2 — 997.1 KiB — 0 ms — font-display: swaphttps://cdn.jsdelivr.net/gh/cormullion/juliamono-webfonts/JuliaMono-Bold.woff2JuliaMono-Bold.woff2 https://cdn.jsdelivr.net/gh/cormullion/juliamono-webfonts/JuliaMono-Bold.woff2 — 998.0 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/roboto/v51/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2KFO7CnqEu92Fr1ME7kSn66a... https://fonts.gstatic.com/s/roboto/v51/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2 — 36.7 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/roboto/v48/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2KFO7CnqEu92Fr1ME7kSn66a... https://fonts.gstatic.com/s/roboto/v48/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2 — 33.9 KiB — 0 ms — font-display: swap
JuliaMono-Regular.woff2 woff2 swap
Size 997 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
JuliaMono-Bold.woff2 woff2 swap
Size 998 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
KFO7CnqEu92Fr1ME7kSn66a... woff2 swap
Size 37 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
KFO7CnqEu92Fr1ME7kSn66a... woff2 swap
Size 34 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 ~998 KB and ~1996 ms

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

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.julialang.org/libs/detectdark.js1 KB—✓1st
https://www.julialang.org/libs/buttons.js7 KB—✓1st
https://plausible.io/js/script.js2 KB—✓3rd
https://kit.fontawesome.com/f030d443fe.js0 KB—✓3rd
https://www.julialang.org/libs/youtube-player.js1 KB—✓1st
https://www.julialang.org/libs/bootstrap/bootstrap.bundle.min.js24 KB—✓1st
https://www.julialang.org/libs/highlight/highlight.min.js17 KB—✓1st
https://www.julialang.org/libs/carousel.js1 KB—✓1st
https://www.youtube.com/iframe_api4 KB—✓3rd
https://www.youtube.com/s/player/57fefa84/www-widgetapi.vflset/www-widgetapi.js11 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+
HTTP Caching
max-age=600 (10 minutes)
PASS
max-age=600 (10 minutes)
Info::
Cache-Control header is set
Got: max-age=600
Info::
Effective TTL: 10 minutes (max-age=600)
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present
Cache-Control

max-age=600

DirectiveValueMeaning
max-age600Cache for 10 minutes
Effective TTL: 600 seconds
Network Waterfall
59 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
27% of JavaScript execution is third-party
First-party Third-party 115ms · 0KB · $2/mo
Unattributable
Other
Optional
Execution 115ms
Transfer 0 KB
Monthly Cost $2/mo

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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