Skip to content
https://python.ca

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
91
GRADE
A
FIX
2
REVIEW
3
PASS
10
INFO
2

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

Mobile Desktop
70
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
75
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.
92
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.

4.30 s

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

5.17 s

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

1 ms

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

0.003

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

4.30 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.

5.17 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
17
10 PASS 3 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 (520.0 KiB of 520.3 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.

B
JS Execution Cost
778ms total JS execution
REVIEW
778ms total JS execution
Warning::
https://www.python.org/: 288ms CPU time
Info::
Unattributable: 249ms CPU time
Info::
https://ajax.googleapis.com/ajax/libs/jquery/1.8.2...: 132ms CPU time
Info::
https://www.python.org/static/js/libs/modernizr.js: 58ms CPU time
Info::
https://ajax.googleapis.com/ajax/libs/jqueryui/1.1...: 51ms CPU time
Warning::
Third-party scripts: 778ms (100% of total)

Main Thread Breakdown

Style & Layout 29% Other 28% Script Evaluation 24% Garbage Collection 6% Parse HTML & CSS 5% Rendering 4% Script Parsing & Compilation 4%
ScriptTotalScriptingParse/CompileParty
https://www.python.org/288ms0ms1ms3rd
Unattributable249ms2ms0ms3rd
https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js132ms96ms7ms3rd
https://www.python.org/static/js/libs/modernizr.js58ms27ms2ms3rd
https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js51ms32ms18ms3rd
B
JS Bundles
10 scripts, 118 KB unused
REVIEW
10 scripts, 118 KB unused
Warning::
https://ajax.googleapis.com/ajax/libs/jqueryui/1.1...: 59 KB unused (89%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://ajax.googleapis.com/ajax/libs/jqueryui/1.1...: 59 KB unused (89%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 118 KB
118 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js66 KB59 KB (89%)✓3rd
https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js0 KB59 KB (89%)✓3rd
https://analytics.python.org/js/script.file-downloads.outbound-links.js2 KB—✓3rd
https://media.ethicalads.io/media/client/v1.4.0/ethicalads.min.js9 KB—✓3rd
https://www.python.org/static/js/libs/modernizr.js5 KB—✓3rd
https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js33 KB—✓3rd
https://www.python.org/static/js/libs/masonry.pkgd.min.js8 KB—✓3rd
https://www.python.org/static/js/libs/html-includes.js0 KB—✓3rd
https://www.python.org/static/js/main-min.e1f3949ae225.js10 KB—✗3rd
https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js0 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
520 KB transferred, 29 requests
PASS
520 KB transferred, 29 requests
Info::
Page weighs 1.1 MB (520 KB transferred)
Info::
29 HTTP requests
Info::
Estimated 0.11 g CO2 per page load
520 KB / 2.4 MB budget
520 KB transferred
29 requests
0.11 g CO2 per page load
CSS 155.9 KiB 30%
Fonts 149.6 KiB 29%
JavaScript 133.3 KiB 26%
HTML 48.8 KiB 9%
Images 15.6 KiB 3%
Other 15.1 KiB 3%
Other 1.6 KiB 0%
Other 299 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
1 images, 0 KB saveable
PASS
1 images, 0 KB saveable
Info::
All images are well-optimized
1 images 16 KB
0 oversized -0 KB
1 legacy format
0 missing dimensions CLS risk
A+
Font Loading
6 fonts (150 KB)
PASS
6 fonts (150 KB)
Info::
6 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

6

150 KB total

Render-blocking

0

of 6

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 5.0 s FCP 4.3 s LCP 5.2 sdata:application/x-font-woff;charset=utf-8;base64,d09GRgABAAAAADDwAAsAAAAAMKQAAQAAAAAAAAAAAAAAAAAAA…x-font-woff;charset=utf... data:application/x-font-woff;charset=utf-8;base64,d09GRgABAAAAADDwAAsAAAAAMKQAAQAAAAAAAAAAAAAAAAAAA… — 12.2 KiB — 33 ms — font-display: swaphttps://www.python.org/static/fonts/SourceSansPro-Regular-webfont.fd0d51605201.woffSourceSansPro-Regular-w... https://www.python.org/static/fonts/SourceSansPro-Regular-webfont.fd0d51605201.woff — 25.9 KiB — 3 ms — font-display: swaphttps://www.python.org/static/fonts/SourceSansPro-Bold-webfont.be855452e565.woffSourceSansPro-Bold-webf... https://www.python.org/static/fonts/SourceSansPro-Bold-webfont.be855452e565.woff — 25.8 KiB — 8 ms — font-display: swaphttps://www.python.org/static/fonts/FluxRegular.f5549a4fe75f.woffFluxRegular.f5549a4fe75... https://www.python.org/static/fonts/FluxRegular.f5549a4fe75f.woff — 29.4 KiB — 11 ms — font-display: swaphttps://www.python.org/static/fonts/SourceSansPro-It-webfont.1aa29ac0f190.woffSourceSansPro-It-webfon... https://www.python.org/static/fonts/SourceSansPro-It-webfont.1aa29ac0f190.woff — 27.6 KiB — 9 ms — font-display: swaphttps://www.python.org/static/fonts/FluxBold.3fd71a747d5c.woffFluxBold.3fd71a747d5c.woff https://www.python.org/static/fonts/FluxBold.3fd71a747d5c.woff — 28.6 KiB — 9 ms — font-display: swap
x-font-woff;charset=utf... woff swap
Size 12 KB
Load time 33 ms
Start 568 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
SourceSansPro-Regular-w... woff swap
Size 26 KB
Load time 3 ms
Start 600 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
SourceSansPro-Bold-webf... woff swap
Size 26 KB
Load time 8 ms
Start 604 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
FluxRegular.f5549a4fe75... woff swap
Size 29 KB
Load time 11 ms
Start 605 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
SourceSansPro-It-webfon... woff swap
Size 28 KB
Load time 9 ms
Start 607 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
FluxBold.3fd71a747d5c.woff woff swap
Size 29 KB
Load time 9 ms
Start 607 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
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 ~45 KB and ~90 ms

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
2 hints, 0 missing preconnects
PASS
2 hints, 0 missing preconnects
Info::
Page uses 2 resource hint(s)

Current Resource Hints

preconnect
—
preload
—
dns-prefetch
—
prefetch
2

2 resource hints configured

A
Page Weight Inventory
29 resources · 520 KB · 118 KB savings available
PASS
29 resources · 520 KB · 118 KB savings available
Info::
Within 1MB page-weight target
Got: 520 KB
Info::
~118 KB of savings available
Warning::
28 third-party resources (100% of weight)
29 resources · 520.3 KiB · 28 third-party Within 1MB page-weight target
CSS 30% · 155.9 KiB
Font 29% · 149.6 KiB
JavaScript 26% · 133.3 KiB
Document 10% · 49.5 KiB
Image 6% · 30.5 KiB
Other 0% · 1.5 KiB

~118.4 KiB of savings available

Remove unused JavaScript: 118.4 KiB
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
29 requests over 1852ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s FCP 4.3 s LCP 5.2 shttps://python.ca// https://python.ca/ — 302 — 247 B — 495 ms — http/1.1http://www.python.org/www.python.org/ http://www.python.org/ — 307 — 0 B — 0 ms — http/1.1https://www.python.org/www.python.org/ https://www.python.org/ — 200 — 48.8 KiB — 13 ms — h2https://analytics.python.org/js/script.file-downloads.outbound-links.jsanalytics.python.org/js/script.file... https://analytics.python.org/js/script.file-downloads.outbound-links.js — 200 — 1.8 KiB — 29 ms — h2https://media.ethicalads.io/media/client/v1.4.0/ethicalads.min.jsmedia.ethicalads.io/media/client/v1... https://media.ethicalads.io/media/client/v1.4.0/ethicalads.min.js — 200 — 8.6 KiB — 108 ms — h2https://www.python.org/static/js/libs/modernizr.jswww.python.org/static/js/libs/moder... https://www.python.org/static/js/libs/modernizr.js — 200 — 5.2 KiB — 10 ms — h2https://www.python.org/static/stylesheets/style.c4f369bed0d3.csswww.python.org/static/stylesheets/s... https://www.python.org/static/stylesheets/style.c4f369bed0d3.css — 200 — 122.7 KiB — 10 ms — h2https://www.python.org/static/stylesheets/mq.a4feecea96fa.csswww.python.org/static/stylesheets/m... https://www.python.org/static/stylesheets/mq.a4feecea96fa.css — 200 — 17.3 KiB — 10 ms — h2https://www.python.org/static/stylesheets/font-awesome.bf0c425cdb73.csswww.python.org/static/stylesheets/f... https://www.python.org/static/stylesheets/font-awesome.bf0c425cdb73.css — 200 — 7.1 KiB — 9 ms — h2https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/themes/smoothness/jquery-ui.cssajax.googleapis.com/ajax/libs/jquer... https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/themes/smoothness/jquery-ui.css — 200 — 8.8 KiB — 95 ms — h2https://www.python.org/static/img/python-logo.pngwww.python.org/static/img/python-lo... https://www.python.org/static/img/python-logo.png — 200 — 15.6 KiB — 9 ms — h2https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.jsajax.googleapis.com/ajax/libs/jquer... https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js — 200 — 33.0 KiB — 122 ms — h2https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.jsajax.googleapis.com/ajax/libs/jquer... https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js — 200 — 66.5 KiB — 134 ms — h2https://www.python.org/static/js/libs/masonry.pkgd.min.jswww.python.org/static/js/libs/mason... https://www.python.org/static/js/libs/masonry.pkgd.min.js — 200 — 7.9 KiB — 5 ms — h2https://www.python.org/static/js/libs/html-includes.jswww.python.org/static/js/libs/html-... https://www.python.org/static/js/libs/html-includes.js — 200 — 291 B — 5 ms — h2https://www.python.org/static/js/main-min.e1f3949ae225.jswww.python.org/static/js/main-min.e... https://www.python.org/static/js/main-min.e1f3949ae225.js — 200 — 10.0 KiB — 4 ms — h2https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.jsajax.googleapis.com/ajax/libs/jquer... https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js — 200 — 0 B — 87 ms — h2https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.jsajax.googleapis.com/ajax/libs/jquer... https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js — 200 — 0 B — 110 ms — h2data:application/x-font-woff;charset=utf-8;base64,d09GRgABAAAAADDwAAsAAAAAMKQAAQAAAAAAAAAAAAAAAAAAA…data:application/x-font-woff;charse... data:application/x-font-woff;charset=utf-8;base64,d09GRgABAAAAADDwAAsAAAAAMKQAAQAAAAAAAAAAAAAAAAAAA… — 200 — 12.2 KiB — 33 ms — datahttps://www.python.org/static/fonts/SourceSansPro-Regular-webfont.fd0d51605201.woffwww.python.org/static/fonts/SourceS... https://www.python.org/static/fonts/SourceSansPro-Regular-webfont.fd0d51605201.woff — 200 — 25.9 KiB — 3 ms — h2https://www.python.org/static/fonts/SourceSansPro-Bold-webfont.be855452e565.woffwww.python.org/static/fonts/SourceS... https://www.python.org/static/fonts/SourceSansPro-Bold-webfont.be855452e565.woff — 200 — 25.8 KiB — 8 ms — h2https://www.python.org/static/fonts/FluxRegular.f5549a4fe75f.woffwww.python.org/static/fonts/FluxReg... https://www.python.org/static/fonts/FluxRegular.f5549a4fe75f.woff — 200 — 29.4 KiB — 11 ms — h2https://www.python.org/static/fonts/SourceSansPro-It-webfont.1aa29ac0f190.woffwww.python.org/static/fonts/SourceS... https://www.python.org/static/fonts/SourceSansPro-It-webfont.1aa29ac0f190.woff — 200 — 27.6 KiB — 9 ms — h2https://www.python.org/static/fonts/FluxBold.3fd71a747d5c.woffwww.python.org/static/fonts/FluxBol... https://www.python.org/static/fonts/FluxBold.3fd71a747d5c.woff — 200 — 28.6 KiB — 9 ms — h2https://www.python.org/authenticatedwww.python.org/authenticated https://www.python.org/authenticated — 200 — 457 B — 2 ms — h2https://analytics.python.org/api/eventanalytics.python.org/api/event https://analytics.python.org/api/event — 202 — 299 B — 469 ms — h3https://console.python.org/python-dot-org-live-consoles-statusconsole.python.org/python-dot-org-l... https://console.python.org/python-dot-org-live-consoles-status — -1 — 0 B — 0 ms — https://2p66nmmycsj3.statuspage.io/api/v2/status.json2p66nmmycsj3.statuspage.io/api/v2/s... https://2p66nmmycsj3.statuspage.io/api/v2/status.json — 200 — 1.2 KiB — 1.1 s — h2https://www.python.org/static/favicon.icowww.python.org/static/favicon.ico https://www.python.org/static/favicon.ico — 200 — 14.9 KiB — 3 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
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 778ms · 54KB · CA$11/mo
www.python.org
Other
Costly
Execution 288ms
Transfer 49 KB
Monthly Cost CA$4/mo
Unattributable
Other
Costly
Execution 249ms
Transfer 0 KB
Monthly Cost CA$3/mo
ajax.googleapis.com
Other
Optional
Execution 132ms
Transfer 0 KB
Monthly Cost CA$2/mo
www.python.org
Other
Optional
Execution 58ms
Transfer 5 KB
Monthly Cost CA$1/mo
ajax.googleapis.com
Other
Optional
Execution 51ms
Transfer 0 KB
Unused 89%
Monthly Cost CA$1/mo

These scripts may cost more than they're worth

  • www.python.org adds 288ms and costs ~CA$4/month
  • Unattributable adds 249ms and costs ~CA$3/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

www.python.org takes 288ms 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

Unattributable takes 249ms 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

89% of ajax.googleapis.com'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.

Send Feedback