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https://rubyonrails.org

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
81
GRADE
B
FIX
2
REVIEW
3
PASS
7
INFO
2

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

98
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.
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.

250 ms

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

973 ms

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

82 ms

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

0.039

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

440 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.

975 ms

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
7 PASS 3 REVIEW 2 FIX
F
Page Weight Budget
Action
2.6 MB transferred, 49 requests
FIX
2.6 MB transferred, 49 requests
Warning::
Page weighs 3.1 MB (2.6 MB transferred)
Info::
49 HTTP requests
Info::
Estimated 0.55 g CO2 per page load
2.6 MB / 2.4 MB budget
2.6 MB transferred
49 requests
0.55 g CO2 per page load
Other 2.0 MiB 75%
Images 475.4 KiB 18%
Fonts 157.9 KiB 6%
Other 25.0 KiB 1%
CSS 10.7 KiB 0%
HTML 5.5 KiB 0%
Other 2.6 KiB 0%
JavaScript 1.9 KiB 0%
Other 504 B 0%
0 2.4 MB 4.9 MB
Over budget
D
Third-Party Impact
Action
91% third-party, 0 ms blocking
FIX
91% third-party, 0 ms blocking
Warning::
Third-party code accounts for 91% of page weight (2.4 MiB of 2.6 MiB)
Info::
Third-party blocking time is low (0 ms)
91%
First-party Third-party
C
Image Optimization
Action
33 images, 0 KB saveable
REVIEW
33 images, 0 KB saveable
Warning::
https://rubyonrails.org/assets/images/logo-hey.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-basecam... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-instaca... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-square.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-heroku.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-freeage... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-shopify... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-dribbbl... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-zendesk... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-interco... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-gusto.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-kicksta... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-soundcl... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-fleetio... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-planets... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-coinbas... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-cookpad... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-doximit... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-1passwo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-github.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-airbnb.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://rubyonrails.org/assets/images/logo-lime.sv... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
33 images 475 KB
0 oversized -0 KB
29 legacy format
22 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

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

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

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

B
JS Execution Cost
554ms total JS execution
REVIEW
554ms total JS execution
Warning::
https://rubyonrails.org/: 352ms CPU time
Info::
Unattributable: 203ms CPU time
Info::
Third-party scripts: 203ms (37% of total)

Main Thread Breakdown

Other 66% Style & Layout 21% Rendering 8%
ScriptTotalScriptingParse/CompileParty
https://rubyonrails.org/352ms2ms0ms1st
Unattributable203ms4ms0ms3rd
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
5 fonts (158 KB)
PASS
5 fonts (158 KB)
Info::
5 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

5

158 KB total

Render-blocking

0

of 5

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s FCP 250 ms LCP 973 mshttps://rubyonrails.org/assets/fonts/calibre-bold.woff2calibre-bold.woff2 https://rubyonrails.org/assets/fonts/calibre-bold.woff2 — 26.8 KiB — 0 ms — font-display: swaphttps://rubyonrails.org/assets/fonts/calibre-semibold.woff2calibre-semibold.woff2 https://rubyonrails.org/assets/fonts/calibre-semibold.woff2 — 26.1 KiB — 0 ms — font-display: swaphttps://rubyonrails.org/assets/fonts/calibre-regular.woff2calibre-regular.woff2 https://rubyonrails.org/assets/fonts/calibre-regular.woff2 — 26.1 KiB — 0 ms — font-display: swaphttps://rubyonrails.org/assets/fonts/IBMPlexMono-Text.woff2IBMPlexMono-Text.woff2 https://rubyonrails.org/assets/fonts/IBMPlexMono-Text.woff2 — 39.3 KiB — 0 ms — font-display: swaphttps://rubyonrails.org/assets/fonts/IBMPlexMono-Medium.woff2IBMPlexMono-Medium.woff2 https://rubyonrails.org/assets/fonts/IBMPlexMono-Medium.woff2 — 39.6 KiB — 0 ms — font-display: swap
calibre-bold.woff2 woff2 swap
Size 27 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
calibre-semibold.woff2 woff2 swap
Size 26 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
calibre-regular.woff2 woff2 swap
Size 26 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
IBMPlexMono-Text.woff2 woff2 swap
Size 39 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
IBMPlexMono-Medium.woff2 woff2 swap
Size 40 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
1 scripts, 0 KB unused
PASS
1 scripts, 0 KB unused
0 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://plausible.io/js/script.js2 KB3rd
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
49 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 203ms · 0KB · $3/mo
Unattributable
Other
Costly
Execution 203ms
Transfer 0 KB
Monthly Cost $3/mo

These scripts may cost more than they're worth

  • Unattributable adds 203ms and costs ~$3/month

Unattributable takes 203ms 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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