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https://getbootstrap.com

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
96
GRADE
A
FIX
0
REVIEW
1
PASS
14
INFO
2

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

Mobile Desktop
99
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
92
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.

1.54 s

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

1.92 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.

0.005

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

1.54 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.

1.93 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
14 PASS 1 REVIEW
B
Image Optimization
8 images, 0 KB saveable
REVIEW
8 images, 0 KB saveable
Warning::
https://srv.carbonads.net/static/30242/c23294fd265... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
8 images 158 KB
0 oversized -0 KB
7 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

A+
Page Weight Budget
313 KB transferred, 22 requests
PASS
313 KB transferred, 22 requests
Info::
Page weighs 815 KB (313 KB transferred)
Info::
22 HTTP requests
Info::
Estimated 0.06 g CO2 per page load
313 KB / 2.4 MB budget
313 KB transferred
22 requests
0.06 g CO2 per page load
Images 158.0 KiB 50%
JavaScript 79.9 KiB 26%
CSS 43.1 KiB 14%
HTML 17.3 KiB 6%
Other 13.4 KiB 4%
Other 945 B 0%
Other 769 B 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Under budget
A
Third-Party Impact
39% third-party, 0 ms blocking
PASS
39% third-party, 0 ms blocking
Info::
Third-party code accounts for 39% of page weight (121.8 KiB of 313.5 KiB)
Info::
Third-party blocking time is low (0 ms)
61%
39%
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+
JS Execution Cost
488ms total JS execution
PASS
488ms total JS execution
Warning::
https://getbootstrap.com/: 262ms CPU time
Info::
Unattributable: 226ms CPU time
Info::
Third-party scripts: 226ms (46% of total)

Main Thread Breakdown

Other 41% Style & Layout 22% Script Evaluation 18% Rendering 11% Parse HTML & CSS 6%
ScriptTotalScriptingParse/CompileParty
https://getbootstrap.com/262ms5ms1ms1st
Unattributable226ms36ms0ms3rd
A+
Font Loading
No web fonts (system fonts)
PASS
No web fonts (system fonts)
Info::
No web fonts loaded — system fonts are fastest
No web fonts loaded — system fonts are optimal.
A+
JS Bundles
6 scripts, 31 KB unused
PASS
6 scripts, 31 KB unused
Warning::
https://getbootstrap.com/docs/5.3/assets/Scripts.a...: 31 KB unused (84%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 31 KB
31 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://getbootstrap.com/docs/5.3/assets/Scripts.astro_astro_type_script_index_0_lang.B072HICR.js38 KB31 KB (84%)✓1st
https://getbootstrap.com/docs/5.3/assets/js/color-modes.js1 KB—✓1st
https://getbootstrap.com/docs/5.3/assets/Code.astro_astro_type_script_index_0_lang.jwvOqc1M.js4 KB—✓1st
https://getbootstrap.com/docs/5.3/dist/js/bootstrap.bundle.min.js24 KB—✓1st
https://cdn.usefathom.com/script.js3 KB—✓3rd
https://cdn.carbonads.com/carbon.js?serve=CKYIKKJL&placement=getbootstrapcom&format=responsive11 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

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
1 hints, 0 missing preconnects
PASS
1 hints, 0 missing preconnects
Info::
Page uses 1 resource hint(s)

Current Resource Hints

preconnect
1
preload
—
dns-prefetch
—
prefetch
—

1 resource hints configured

A+
Page Weight Inventory
22 resources · 313 KB · 31 KB savings available
PASS
22 resources · 313 KB · 31 KB savings available
Info::
Within 1MB page-weight target
Got: 313 KB
Info::
8 third-party resources (39% of weight)
22 resources · 313.5 KiB · 8 third-party Within 1MB page-weight target
Image 55% · 171.4 KiB
JavaScript 26% · 79.9 KiB
CSS 14% · 43.1 KiB
Document 6% · 17.3 KiB
Other 1% · 1.7 KiB

~31.3 KiB of savings available

Remove unused JavaScript: 31.3 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
A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

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
22 requests over 632ms
INFO
0 ms 500 ms 1.0 s 1.5 s 2.0 s FCP 1.5 s LCP 1.9 shttps://getbootstrap.com// https://getbootstrap.com/ — 200 — 17.3 KiB — 92 ms — h2https://getbootstrap.com/docs/5.3/assets/js/color-modes.js/docs/5.3/assets/js/color-modes.js https://getbootstrap.com/docs/5.3/assets/js/color-modes.js — 200 — 1.1 KiB — 34 ms — h2https://getbootstrap.com/docs/5.3/dist/css/bootstrap.min.css/docs/5.3/dist/css/bootstrap.min.cs... https://getbootstrap.com/docs/5.3/dist/css/bootstrap.min.css — 200 — 31.4 KiB — 35 ms — h2https://getbootstrap.com/docs/5.3/assets/_slug_.CJzlHdSW.css/docs/5.3/assets/_slug_.CJzlHdSW.cs... https://getbootstrap.com/docs/5.3/assets/_slug_.CJzlHdSW.css — 200 — 11.7 KiB — 32 ms — h2https://getbootstrap.com/docs/5.3/assets/brand/bootstrap-logo-shadow@2x.png/docs/5.3/assets/brand/bootstrap-lo... https://getbootstrap.com/docs/5.3/assets/brand/bootstrap-logo-shadow@2x.png — 200 — 42.1 KiB — 60 ms — h2https://getbootstrap.com/docs/5.3/assets/Code.astro_astro_type_script_index_0_lang.jwvOqc1M.js/docs/5.3/assets/Code.astro_astro_t... https://getbootstrap.com/docs/5.3/assets/Code.astro_astro_type_script_index_0_lang.jwvOqc1M.js — 200 — 4.1 KiB — 46 ms — h2https://getbootstrap.com/docs/5.3/dist/js/bootstrap.bundle.min.js/docs/5.3/dist/js/bootstrap.bundle.... https://getbootstrap.com/docs/5.3/dist/js/bootstrap.bundle.min.js — 200 — 23.8 KiB — 48 ms — h2https://getbootstrap.com/docs/5.3/assets/Scripts.astro_astro_type_script_index_0_lang.B072HICR.js/docs/5.3/assets/Scripts.astro_astr... https://getbootstrap.com/docs/5.3/assets/Scripts.astro_astro_type_script_index_0_lang.B072HICR.js — 200 — 37.7 KiB — 44 ms — h2https://cdn.usefathom.com/script.jscdn.usefathom.com/script.js https://cdn.usefathom.com/script.js — 200 — 2.7 KiB — 230 ms — h2https://cdn.carbonads.com/carbon.js?serve=CKYIKKJL&placement=getbootstrapcom&format=responsivecdn.carbonads.com/carbon.js?serve=C... https://cdn.carbonads.com/carbon.js?serve=CKYIKKJL&placement=getbootstrapcom&format=responsive — 200 — 10.6 KiB — 96 ms — h2data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='%23000'%3e%3…www.w3.org/2000/svg' viewBox='0 0 1... data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='%23000'%3e%3… — 200 — 0 B — 0 ms — datahttps://getbootstrap.com/docs/5.3/assets/img/webpack.svg/docs/5.3/assets/img/webpack.svg https://getbootstrap.com/docs/5.3/assets/img/webpack.svg — 200 — 827 B — 49 ms — h3https://getbootstrap.com/docs/5.3/assets/img/parcel.png/docs/5.3/assets/img/parcel.png https://getbootstrap.com/docs/5.3/assets/img/parcel.png — 200 — 6.4 KiB — 29 ms — h3https://getbootstrap.com/docs/5.3/assets/img/vite.svg/docs/5.3/assets/img/vite.svg https://getbootstrap.com/docs/5.3/assets/img/vite.svg — 200 — 1.1 KiB — 43 ms — h3https://getbootstrap.com/docs/5.3/assets/img/favicons/manifest.json/docs/5.3/assets/img/favicons/manif... https://getbootstrap.com/docs/5.3/assets/img/favicons/manifest.json — 200 — 769 B — 146 ms — h3https://srv.carbonads.net/ads/CKYIKKJL.json?segment=placement:getbootstrapcom&v=truesrv.carbonads.net/ads/CKYIKKJL.json... https://srv.carbonads.net/ads/CKYIKKJL.json?segment=placement:getbootstrapcom&v=true — 200 — 0 B — 159 ms — h2https://cdn.usefathom.com/?h=https%3A%2F%2Fgetbootstrap.com&p=%2F&r=&sid=ITUSEYJG&qs=%7B%7D&cid=38662313cdn.usefathom.com/?h=https%3A%2F%2F... https://cdn.usefathom.com/?h=https%3A%2F%2Fgetbootstrap.com&p=%2F&r=&sid=ITUSEYJG&qs=%7B%7D&cid=38662313 — 200 — 434 B — 157 ms — h2https://getbootstrap.com/docs/5.3/assets/img/favicons/favicon.ico/docs/5.3/assets/img/favicons/favic... https://getbootstrap.com/docs/5.3/assets/img/favicons/favicon.ico — 200 — 5.0 KiB — 46 ms — h3https://getbootstrap.com/docs/5.3/assets/img/favicons/android-chrome-192x192.png/docs/5.3/assets/img/favicons/andro... https://getbootstrap.com/docs/5.3/assets/img/favicons/android-chrome-192x192.png — 200 — 8.4 KiB — 57 ms — h3https://srv.carbonads.net/ads/CKYIKKJL.json?segment=placement:getbootstrapcom&v=truesrv.carbonads.net/ads/CKYIKKJL.json... https://srv.carbonads.net/ads/CKYIKKJL.json?segment=placement:getbootstrapcom&v=true — 200 — 945 B — 34 ms — h2https://srv.carbonads.net/static/30242/9f65de4d860c516a1d5ba16a54be72612f499c35srv.carbonads.net/static/30242/9f65... https://srv.carbonads.net/static/30242/9f65de4d860c516a1d5ba16a54be72612f499c35 — 200 — 103.7 KiB — 180 ms — h2https://srv.carbonads.net/static/30242/c23294fd2651b625306973f79ea8c38730ba76a9srv.carbonads.net/static/30242/c232... https://srv.carbonads.net/static/30242/c23294fd2651b625306973f79ea8c38730ba76a9 — 200 — 3.5 KiB — 179 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
46% of JavaScript execution is third-party
First-party Third-party 226ms · 0KB · $3/mo
Unattributable
Other
Costly
Execution 226ms
Transfer 0 KB
Monthly Cost $3/mo

These scripts may cost more than they're worth

  • Unattributable adds 226ms and costs ~$3/month

46% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

Learn more ▾

Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

Unattributable takes 226ms 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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