Skip to content
https://pypi.org

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
95
GRADE
A
FIX
1
REVIEW
4
PASS
10
INFO
2

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

Mobile Desktop
71
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.
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.

1.80 s

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

3.12 s

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

35 ms

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

0.501

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

1.80 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.

3.89 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 4 REVIEW 1 FIX
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.
Info::
ETag present — enables conditional (304) responses

No Cache-Control header

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

B
Image Optimization
2 images, 0 KB saveable
REVIEW
2 images, 0 KB saveable
Warning::
https://pypi.org/static/images/white-cube.2351a86c... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://pypi.org/static/images/logo-small.8998e9d1... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
2 images 53 KB
0 oversized -0 KB
2 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 Execution Cost
646ms total JS execution
REVIEW
646ms total JS execution
Warning::
https://pypi.org/: 257ms CPU time
Info::
Unattributable: 182ms CPU time
Info::
https://pypi.org/static/js/warehouse.e9abdc3b.js: 134ms CPU time
Info::
https://analytics.python.org/js/script.js: 73ms CPU time
Info::
Third-party scripts: 255ms (40% of total)

Main Thread Breakdown

Style & Layout 35% Other 29% Script Evaluation 23% Rendering 5% Parse HTML & CSS 4%
ScriptTotalScriptingParse/CompileParty
https://pypi.org/257ms6ms1ms1st
Unattributable182ms8ms0ms3rd
https://pypi.org/static/js/warehouse.e9abdc3b.js134ms118ms14ms1st
https://analytics.python.org/js/script.js73ms16ms2ms3rd
B
JS Bundles
3 scripts, 66 KB unused
REVIEW
3 scripts, 66 KB unused
Warning::
https://pypi.org/static/js/warehouse.e9abdc3b.js: 66 KB unused (63%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 66 KB
66 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://pypi.org/static/js/warehouse.e9abdc3b.js105 KB66 KB (63%)✓1st
https://analytics.python.org/js/script.js2 KB—✓3rd
https://media.ethicalads.io/media/client/v1.4.0/ethicalads.min.js9 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

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Page Weight Budget
521 KB transferred, 19 requests
PASS
521 KB transferred, 19 requests
Info::
Page weighs 547 KB (521 KB transferred)
Info::
19 HTTP requests
Info::
Estimated 0.11 g CO2 per page load
521 KB / 2.4 MB budget
521 KB transferred
19 requests
0.11 g CO2 per page load
CSS 174.3 KiB 33%
Fonts 161.5 KiB 31%
JavaScript 115.5 KiB 22%
Images 53.1 KiB 10%
HTML 6.8 KiB 1%
Other 6.2 KiB 1%
Other 4.1 KiB 1%
0 2.4 MB 4.9 MB
Under budget
A+
Third-Party Impact
2% third-party, 0 ms blocking
PASS
2% third-party, 0 ms blocking
Info::
Third-party code accounts for 2% of page weight (11.7 KiB of 521.5 KiB)
Info::
Third-party blocking time is low (0 ms)
98%
First-party Third-party
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 (161 KB)
PASS
5 fonts (161 KB)
Info::
5 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

5

161 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 1.0 s 2.0 s 3.0 s FCP 1.8 s LCP 3.1 shttps://pypi.org/static/webfonts/source-sans-3-latin-400-normal.5e0fb0b8.woff2source-sans-3-latin-400... https://pypi.org/static/webfonts/source-sans-3-latin-400-normal.5e0fb0b8.woff2 — 15.5 KiB — 10 ms — font-display: swaphttps://pypi.org/static/webfonts/fa-solid-900.ce9a3fa7.woff2fa-solid-900.ce9a3fa7.w... https://pypi.org/static/webfonts/fa-solid-900.ce9a3fa7.woff2 — 112.3 KiB — 16 ms — font-display: swaphttps://pypi.org/static/webfonts/source-sans-3-latin-600-normal.7dc998af.woff2source-sans-3-latin-600... https://pypi.org/static/webfonts/source-sans-3-latin-600-normal.7dc998af.woff2 — 15.5 KiB — 14 ms — font-display: swaphttps://pypi.org/static/webfonts/source-sans-3-cyrillic-400-normal.b88e2831.woff2source-sans-3-cyrillic-... https://pypi.org/static/webfonts/source-sans-3-cyrillic-400-normal.b88e2831.woff2 — 10.2 KiB — 6 ms — font-display: swaphttps://pypi.org/static/webfonts/source-sans-3-greek-400-normal.034ea2f2.woff2source-sans-3-greek-400... https://pypi.org/static/webfonts/source-sans-3-greek-400-normal.034ea2f2.woff2 — 8.0 KiB — 7 ms — font-display: swap
source-sans-3-latin-400... woff2 swap
Size 16 KB
Load time 10 ms
Start 111 ms
Risk FOUT — text flashes from fallback to web font
fa-solid-900.ce9a3fa7.w... woff2 swap
Size 112 KB
Load time 16 ms
Start 111 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
source-sans-3-latin-600... woff2 swap
Size 15 KB
Load time 14 ms
Start 111 ms
Risk FOUT — text flashes from fallback to web font
source-sans-3-cyrillic-... woff2 swap
Size 10 KB
Load time 6 ms
Start 111 ms
Risk FOUT — text flashes from fallback to web font
source-sans-3-greek-400... woff2 swap
Size 8 KB
Load time 7 ms
Start 112 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 ~56 KB and ~112 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
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
A+
Page Weight Inventory
19 resources · 521 KB · 66 KB savings available
PASS
19 resources · 521 KB · 66 KB savings available
Info::
Within 1MB page-weight target
Got: 521 KB
Info::
~66 KB of savings available
Info::
4 third-party resources (2% of weight)
19 resources · 521.5 KiB · 4 third-party Within 1MB page-weight target
CSS 33% · 174.3 KiB
Font 31% · 161.5 KiB
JavaScript 22% · 115.5 KiB
Image 11% · 57.2 KiB
Document 2% · 11.5 KiB
Other 0% · 1.5 KiB

~66.4 KiB of savings available

Remove unused JavaScript: 66.4 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
19 requests over 290ms
INFO
0 ms 1.0 s 2.0 s 3.0 s FCP 1.8 s LCP 3.1 shttps://pypi.org// https://pypi.org/ — 200 — 6.8 KiB — 15 ms — h2https://pypi.org/static/css/warehouse-ltr.0f58843e.css/static/css/warehouse-ltr.0f58843e.... https://pypi.org/static/css/warehouse-ltr.0f58843e.css — 200 — 88.0 KiB — 16 ms — h2https://pypi.org/static/css/fontawesome.379f9724.css/static/css/fontawesome.379f9724.cs... https://pypi.org/static/css/fontawesome.379f9724.css — 200 — 68.7 KiB — 18 ms — h2https://pypi.org/static/css/fonts.3b5d1a1c.css/static/css/fonts.3b5d1a1c.css https://pypi.org/static/css/fonts.3b5d1a1c.css — 200 — 17.7 KiB — 19 ms — h2https://pypi.org/static/images/logo-small.8998e9d1.svg/static/images/logo-small.8998e9d1.... https://pypi.org/static/images/logo-small.8998e9d1.svg — 200 — 51.9 KiB — 17 ms — h2https://pypi.org/static/images/white-cube.2351a86c.svg/static/images/white-cube.2351a86c.... https://pypi.org/static/images/white-cube.2351a86c.svg — 200 — 1.2 KiB — 17 ms — h2https://pypi.org/static/js/warehouse.e9abdc3b.js/static/js/warehouse.e9abdc3b.js https://pypi.org/static/js/warehouse.e9abdc3b.js — 200 — 105.3 KiB — 24 ms — h2https://analytics.python.org/js/script.jsanalytics.python.org/js/script.js https://analytics.python.org/js/script.js — 200 — 1.5 KiB — 36 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 — 8.7 KiB — 46 ms — h2https://pypi.org/static/webfonts/source-sans-3-latin-400-normal.5e0fb0b8.woff2/static/webfonts/source-sans-3-lati... https://pypi.org/static/webfonts/source-sans-3-latin-400-normal.5e0fb0b8.woff2 — 200 — 15.5 KiB — 10 ms — h2https://pypi.org/static/webfonts/fa-solid-900.ce9a3fa7.woff2/static/webfonts/fa-solid-900.ce9a3... https://pypi.org/static/webfonts/fa-solid-900.ce9a3fa7.woff2 — 200 — 112.3 KiB — 16 ms — h2https://pypi.org/static/webfonts/source-sans-3-latin-600-normal.7dc998af.woff2/static/webfonts/source-sans-3-lati... https://pypi.org/static/webfonts/source-sans-3-latin-600-normal.7dc998af.woff2 — 200 — 15.5 KiB — 14 ms — h2https://pypi.org/static/webfonts/source-sans-3-cyrillic-400-normal.b88e2831.woff2/static/webfonts/source-sans-3-cyri... https://pypi.org/static/webfonts/source-sans-3-cyrillic-400-normal.b88e2831.woff2 — 200 — 10.2 KiB — 6 ms — h2https://pypi.org/static/webfonts/source-sans-3-greek-400-normal.034ea2f2.woff2/static/webfonts/source-sans-3-gree... https://pypi.org/static/webfonts/source-sans-3-greek-400-normal.034ea2f2.woff2 — 200 — 8.0 KiB — 7 ms — h2https://pypi.org/_includes/unauthed/notification-banners//_includes/unauthed/notification-ba... https://pypi.org/_includes/unauthed/notification-banners/ — 200 — 2.8 KiB — 9 ms — h2https://pypi.org/_includes/unauthed/flash-messages//_includes/unauthed/flash-messages/ https://pypi.org/_includes/unauthed/flash-messages/ — 200 — 1.9 KiB — 101 ms — h2https://2p66nmmycsj3.statuspage.io/api/v2/status.json2p66nmmycsj3.statuspage.io/api/v2/s... https://2p66nmmycsj3.statuspage.io/api/v2/status.json — 200 — 1.2 KiB — 20 ms — h2https://analytics.python.org/api/eventanalytics.python.org/api/event https://analytics.python.org/api/event — 202 — 294 B — 134 ms — h3https://pypi.org/static/images/favicon.35549fe8.ico/static/images/favicon.35549fe8.ico https://pypi.org/static/images/favicon.35549fe8.ico — 200 — 4.1 KiB — 4 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
40% of JavaScript execution is third-party
First-party Third-party 255ms · 2KB · €3/mo
Unattributable
Other
Optional
Execution 182ms
Transfer 0 KB
Monthly Cost €2/mo
analytics.python.org
Other
Optional
Execution 73ms
Transfer 2 KB
Monthly Cost €1/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.

Send Feedback