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https://www.clojure.org

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
90
GRADE
A
FIX
1
REVIEW
4
PASS
7
INFO
2

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

Mobile Desktop
80
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
81
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.
83
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.

871 ms

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

871 ms

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.

0.393

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

871 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.

871 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 4 REVIEW 1 FIX
D
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.
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

B
Third-Party Impact
48% third-party, 0 ms blocking
REVIEW
48% third-party, 0 ms blocking
Info::
Third-party code accounts for 48% of page weight (151.7 KiB of 318.1 KiB)
Info::
Third-party blocking time is low (0 ms)
52%
48%
First-party Third-party
B
Image Optimization
4 images, 0 KB saveable
REVIEW
4 images, 0 KB saveable
Warning::
https://www.clojure.org/images/clojure-logo-120b.p... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.clojure.org/images/clojuretv.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
4 images 88 KB
0 oversized -0 KB
4 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

B
JS Bundles
6 scripts, 53 KB unused
REVIEW
6 scripts, 53 KB unused
Warning::
https://cdn.matomo.cloud/cognitect.matomo.cloud/ma...: 33 KB unused (58%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.clojure.org/js/webflow.js: 20 KB unused (57%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.clojure.org/js/webflow.js: unminified — 13 KB could be saved
Info::
Total unused JavaScript: 53 KB
53 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://cdn.matomo.cloud/cognitect.matomo.cloud/matomo.js57 KB33 KB (58%)✓3rd
https://www.clojure.org/js/webflow.js35 KB20 KB (57%)✗1st
https://www.clojure.org/js/modernizr.js3 KB—✓1st
https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js33 KB—✓3rd
https://www.clojure.org/js/highlight.pack.js12 KB—✓1st
https://cognitect.matomo.cloud/plugins/HeatmapSessionRecording/configs.php?idsite=9&trackerid=xVYZDg&url=https%3A%2F%2Fwww.clojure.org%2F0 KB—✓3rd

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+
Page Weight Budget
318 KB transferred, 25 requests
PASS
318 KB transferred, 25 requests
Info::
Page weighs 783 KB (318 KB transferred)
Info::
25 HTTP requests
Info::
Estimated 0.07 g CO2 per page load
318 KB / 2.4 MB budget
318 KB transferred
25 requests
0.07 g CO2 per page load
JavaScript 140.1 KiB 44%
Images 88.2 KiB 28%
Fonts 58.0 KiB 18%
CSS 21.3 KiB 7%
HTML 6.3 KiB 2%
Other 2.4 KiB 1%
Other 1.7 KiB 1%
Other 145 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+
JS Execution Cost
135ms total JS execution
PASS
135ms total JS execution
Info::
https://www.clojure.org/: 83ms CPU time
Info::
https://cdn.matomo.cloud/cognitect.matomo.cloud/ma...: 52ms CPU time
Info::
Third-party scripts: 52ms (39% of total)

Main Thread Breakdown

Script Evaluation 39% Style & Layout 30% Other 18% Script Parsing & Compilation 7% Rendering 4%
ScriptTotalScriptingParse/CompileParty
https://www.clojure.org/83ms1ms0ms1st
https://cdn.matomo.cloud/cognitect.matomo.cloud/matomo.js52ms45ms6ms3rd
A+
Font Loading
3 fonts (58 KB)
PASS
3 fonts (58 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

58 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 FCP 871 ms LCP 871 mshttps://fonts.gstatic.com/s/opensans/v44/memvYaGs126MiZpBA-UvWbX2vVnXBbObj2OVTS-mu0SC55I.woff2memvYaGs126MiZpBA-UvWbX... https://fonts.gstatic.com/s/opensans/v44/memvYaGs126MiZpBA-UvWbX2vVnXBbObj2OVTS-mu0SC55I.woff2 — 42.0 KiB — 0 ms — font-display: swaphttps://www.clojure.org/fonts/icofont.woff2icofont.woff2 https://www.clojure.org/fonts/icofont.woff2 — 2.1 KiB — 0 ms — font-display: swaphttps://fonts.gstatic.com/s/ptserif/v19/EJRTQgYoZZY2vCFuvAFT_r21cgT9rcs.woff2EJRTQgYoZZY2vCFuvAFT_r2... https://fonts.gstatic.com/s/ptserif/v19/EJRTQgYoZZY2vCFuvAFT_r21cgT9rcs.woff2 — 13.9 KiB — 0 ms — font-display: swap
memvYaGs126MiZpBA-UvWbX... woff2 swap
Size 42 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
icofont.woff2 woff2 swap
Size 2 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
EJRTQgYoZZY2vCFuvAFT_r2... woff2 swap
Size 14 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+
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
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
39% of JavaScript execution is third-party
First-party Third-party 52ms · 57KB · €1/mo
Matomo
Analytics
Optional
Execution 52ms
Transfer 57 KB
Unused 58%
Monthly Cost €1/mo

58% of Matomo'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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