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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
78
GRADE
C
FIX
1
REVIEW
4
PASS
7
INFO
2

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

Mobile Desktop
67
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
94
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.

2.43 s

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

3.53 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.

0.036

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

2.43 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.

3.59 s

Page Load Progression

391 ms
781 ms
1.2 s
1.6 s
2.0 s
2.3 s
2.7 s
3.1 s
Checks
14
7 PASS 4 REVIEW 1 FIX
F
Page Weight Budget
Action
4.2 MB transferred, 89 requests
FIX
4.2 MB transferred, 89 requests
Critical::
Page weighs 6.0 MB (4.2 MB transferred)
Info::
Fonts are 2.3 MB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 2.3 MB
Warning::
Images are 1.7 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 1.7 MB
Info::
89 HTTP requests
Info::
Estimated 0.88 g CO2 per page load
4.2 MB / 2.4 MB budget
4.2 MB transferred
89 requests
0.88 g CO2 per page load
Fonts 2.3 MiB 55%
Images 1.7 MiB 41%
CSS 134.7 KiB 3%
HTML 13.8 KiB 0%
JavaScript 8.5 KiB 0%
Other 3.0 KiB 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

B
Third-Party Impact
58% third-party, 0 ms blocking
REVIEW
58% third-party, 0 ms blocking
Warning::
Third-party code accounts for 58% of page weight (2.4 MiB of 4.2 MiB)
Info::
Third-party blocking time is low (0 ms)
42%
58%
First-party Third-party
B
Image Optimization
62 images, 0 KB saveable
REVIEW
62 images, 0 KB saveable
Warning::
https://www.ruby-lang.org/images/footer/happy-hack... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
62 images 1.7 MB
0 oversized -0 KB
62 legacy format
1 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

C
JS Execution Cost
Action
1045ms total JS execution
REVIEW
1045ms total JS execution
Warning::
https://www.ruby-lang.org/en/: 654ms CPU time
Warning::
Unattributable: 390ms CPU time
Info::
Third-party scripts: 390ms (37% of total)

Main Thread Breakdown

Other 41% Style & Layout 37% Rendering 16% Script Evaluation 4%
ScriptTotalScriptingParse/CompileParty
https://www.ruby-lang.org/en/654ms24ms1ms1st
Unattributable390ms3ms0ms3rd
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
15 fonts (2374 KB)
PASS
15 fonts (2374 KB)
Info::
15 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

15

2374 KB total

Render-blocking

0

of 15

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 2.4 s LCP 3.5 shttps://fonts.gstatic.com/s/materialsymbolsrounded/v325/sykO-zNym6YjUruM-QrEh7-nyTnjDwKNJ_190FjpZIvDmUSVOK7BDB_Qb9vUSzq3wzLK-P0J-UXXkRzDgw.woff2sykO-zNym6YjUruM-QrEh7-... https://fonts.gstatic.com/s/materialsymbolsrounded/v325/sykO-zNym6YjUruM-QrEh7-nyTnjDwKNJ_190FjpZIvDmUSVOK7BDB_Qb9vUSzq3wzLK-P0J-UXXkRzDgw.woff2 — 1.8 MiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/plusjakartasans/v12/LDIoaomQNQcsA88c7O9yZ4KMCoOg4Ko20yygg_vb.woff2LDIoaomQNQcsA88c7O9yZ4K... https://fonts.gstatic.com/s/plusjakartasans/v12/LDIoaomQNQcsA88c7O9yZ4KMCoOg4Ko20yygg_vb.woff2 — 26.7 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/plusjakartasans/v12/LDIuaomQNQcsA88c7O9yZ4KMCoOg4Koz4y6qhNnZR-A.woff2LDIuaomQNQcsA88c7O9yZ4K... https://fonts.gstatic.com/s/plusjakartasans/v12/LDIuaomQNQcsA88c7O9yZ4KMCoOg4Koz4y6qhNnZR-A.woff2 — 28.9 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosansjp/v56/-F62fjtqLzI2JPCgQBnw7HFowwII2lcnk-AFfrgQrvWXpdFg3KXxAMsKMbdN.118.woff2-F62fjtqLzI2JPCgQBnw7HF... https://fonts.gstatic.com/s/notosansjp/v56/-F62fjtqLzI2JPCgQBnw7HFowwII2lcnk-AFfrgQrvWXpdFg3KXxAMsKMbdN.118.woff2 — 18.0 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosansjp/v56/-F62fjtqLzI2JPCgQBnw7HFowwII2lcnk-AFfrgQrvWXpdFg3KXxAMsKMbdN.117.woff2-F62fjtqLzI2JPCgQBnw7HF... https://fonts.gstatic.com/s/notosansjp/v56/-F62fjtqLzI2JPCgQBnw7HFowwII2lcnk-AFfrgQrvWXpdFg3KXxAMsKMbdN.117.woff2 — 11.5 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosansjp/v56/-F62fjtqLzI2JPCgQBnw7HFowwII2lcnk-AFfrgQrvWXpdFg3KXxAMsKMbdN.113.woff2-F62fjtqLzI2JPCgQBnw7HF... https://fonts.gstatic.com/s/notosansjp/v56/-F62fjtqLzI2JPCgQBnw7HFowwII2lcnk-AFfrgQrvWXpdFg3KXxAMsKMbdN.113.woff2 — 14.5 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosanskr/v39/PbykFmXiEBPT4ITbgNA5Cgm203Tq4JJWq209pU0DPdWuqxJFA4GNDCBYtw.118.woff2PbykFmXiEBPT4ITbgNA5Cgm... https://fonts.gstatic.com/s/notosanskr/v39/PbykFmXiEBPT4ITbgNA5Cgm203Tq4JJWq209pU0DPdWuqxJFA4GNDCBYtw.118.woff2 — 14.4 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosanskr/v39/PbykFmXiEBPT4ITbgNA5Cgm203Tq4JJWq209pU0DPdWuqxJFA4GNDCBYtw.117.woff2PbykFmXiEBPT4ITbgNA5Cgm... https://fonts.gstatic.com/s/notosanskr/v39/PbykFmXiEBPT4ITbgNA5Cgm203Tq4JJWq209pU0DPdWuqxJFA4GNDCBYtw.117.woff2 — 14.1 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/plusjakartasans/v12/LDIoaomQNQcsA88c7O9yZ4KMCoOg4Ko50yygg_vbd-E.woff2LDIoaomQNQcsA88c7O9yZ4K... https://fonts.gstatic.com/s/plusjakartasans/v12/LDIoaomQNQcsA88c7O9yZ4KMCoOg4Ko50yygg_vbd-E.woff2 — 8.1 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosanssc/v40/k3kXo84MPvpLmixcA63oeALhLIiP-Q-87KaAaH7rzeAODp22mF0qmF4CSjmPC6A0Rg5g1igg1w.119.woff2k3kXo84MPvpLmixcA63oeAL... https://fonts.gstatic.com/s/notosanssc/v40/k3kXo84MPvpLmixcA63oeALhLIiP-Q-87KaAaH7rzeAODp22mF0qmF4CSjmPC6A0Rg5g1igg1w.119.woff2 — 74.9 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosanssc/v40/k3kXo84MPvpLmixcA63oeALhLIiP-Q-87KaAaH7rzeAODp22mF0qmF4CSjmPC6A0Rg5g1igg1w.118.woff2k3kXo84MPvpLmixcA63oeAL... https://fonts.gstatic.com/s/notosanssc/v40/k3kXo84MPvpLmixcA63oeALhLIiP-Q-87KaAaH7rzeAODp22mF0qmF4CSjmPC6A0Rg5g1igg1w.118.woff2 — 45.1 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosanssc/v40/k3kXo84MPvpLmixcA63oeALhLIiP-Q-87KaAaH7rzeAODp22mF0qmF4CSjmPC6A0Rg5g1igg1w.117.woff2k3kXo84MPvpLmixcA63oeAL... https://fonts.gstatic.com/s/notosanssc/v40/k3kXo84MPvpLmixcA63oeALhLIiP-Q-87KaAaH7rzeAODp22mF0qmF4CSjmPC6A0Rg5g1igg1w.117.woff2 — 51.3 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosanstc/v39/-nF7OG829Oofr2wohFbTp9iFOisNA_cTyNromxqQuEMQ2wHYwbnmy1R1jDujLebozBXCo2qYhRo.119.woff2-nF7OG829Oofr2wohFbTp9i... https://fonts.gstatic.com/s/notosanstc/v39/-nF7OG829Oofr2wohFbTp9iFOisNA_cTyNromxqQuEMQ2wHYwbnmy1R1jDujLebozBXCo2qYhRo.119.woff2 — 33.8 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosanstc/v39/-nF7OG829Oofr2wohFbTp9iFOisNA_cTyNromxqQuEMQ2wHYwbnmy1R1jDujLebozBXCo2qYhRo.118.woff2-nF7OG829Oofr2wohFbTp9i... https://fonts.gstatic.com/s/notosanstc/v39/-nF7OG829Oofr2wohFbTp9iFOisNA_cTyNromxqQuEMQ2wHYwbnmy1R1jDujLebozBXCo2qYhRo.118.woff2 — 58.8 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/notosanstc/v39/-nF7OG829Oofr2wohFbTp9iFOisNA_cTyNromxqQuEMQ2wHYwbnmy1R1jDujLebozBXCo2qYhRo.114.woff2-nF7OG829Oofr2wohFbTp9i... https://fonts.gstatic.com/s/notosanstc/v39/-nF7OG829Oofr2wohFbTp9iFOisNA_cTyNromxqQuEMQ2wHYwbnmy1R1jDujLebozBXCo2qYhRo.114.woff2 — 83.1 KiB — 0 ms — font-display: swap
sykO-zNym6YjUruM-QrEh7-... woff2 swap
Size 1891 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
LDIoaomQNQcsA88c7O9yZ4K... woff2 swap
Size 27 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
LDIuaomQNQcsA88c7O9yZ4K... woff2 swap
Size 29 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
-F62fjtqLzI2JPCgQBnw7HF... woff2 swap
Size 18 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
-F62fjtqLzI2JPCgQBnw7HF... woff2 swap
Size 12 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
-F62fjtqLzI2JPCgQBnw7HF... woff2 swap
Size 15 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
PbykFmXiEBPT4ITbgNA5Cgm... woff2 swap
Size 14 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
PbykFmXiEBPT4ITbgNA5Cgm... woff2 swap
Size 14 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
LDIoaomQNQcsA88c7O9yZ4K... woff2 swap
Size 8 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
k3kXo84MPvpLmixcA63oeAL... woff2 swap
Size 75 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
k3kXo84MPvpLmixcA63oeAL... woff2 swap
Size 45 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
k3kXo84MPvpLmixcA63oeAL... woff2 swap
Size 51 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
-nF7OG829Oofr2wohFbTp9i... woff2 swap
Size 34 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
-nF7OG829Oofr2wohFbTp9i... woff2 swap
Size 59 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
-nF7OG829Oofr2wohFbTp9i... woff2 swap
Size 83 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 ~945 KB and ~1890 ms

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

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.ruby-lang.org/javascripts/navigation-toggle.js1 KB—✓1st
https://www.ruby-lang.org/javascripts/header-navigation.js1 KB—✓1st
https://www.ruby-lang.org/javascripts/toc.js2 KB—✓1st
https://www.ruby-lang.org/javascripts/theme-toggle.js1 KB—✓1st
https://www.ruby-lang.org/javascripts/try-ruby-examples.js1 KB—✓1st
https://www.ruby-lang.org/javascripts/hero-animation.js3 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
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
89 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
37% of JavaScript execution is third-party
First-party Third-party 390ms · 0KB · $5/mo
Unattributable
Other
Costly
Execution 390ms
Transfer 0 KB
Monthly Cost $5/mo

These scripts may cost more than they're worth

  • Unattributable adds 390ms and costs ~$5/month

Unattributable takes 390ms 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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