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https://centos.org

Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
80
GRADE
B
FIX
4
REVIEW
3
PASS
6
INFO
2

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

Mobile Desktop
81
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
98
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.
82
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.

1.09 s

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

2.99 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.

0.004

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

1.09 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.

3.02 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
15
6 PASS 3 REVIEW 4 FIX
F
Page Weight Budget
Action
2.7 MB transferred, 63 requests
FIX
2.7 MB transferred, 63 requests
Warning::
Page weighs 2.9 MB (2.7 MB transferred)
Warning::
Images are 1.9 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 1.9 MB
Info::
CSS is 324 KB — consider purging unused styles
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
Got: 324 KB
Info::
Fonts are 306 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 306 KB
Info::
63 HTTP requests
Info::
Estimated 0.57 g CO2 per page load
2.7 MB / 2.4 MB budget
2.7 MB transferred
63 requests
0.57 g CO2 per page load
Images 1.9 MiB 71%
CSS 323.7 KiB 12%
Fonts 306.1 KiB 11%
JavaScript 117.0 KiB 4%
HTML 42.0 KiB 2%
Other 17.3 KiB 1%
Other 2.1 KiB 0%
0 2.4 MB 4.9 MB
Over budget

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Why this matters

Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.

Source: web.dev

Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.

Why this matters

CSS bundle is large — purge unused styles (PurgeCSS, Tailwind JIT) to reduce CSS payload.

Source: web.dev

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

D
Third-Party Impact
Action
98% third-party, 0 ms blocking
FIX
98% third-party, 0 ms blocking
Warning::
Third-party code accounts for 98% of page weight (2.7 MiB of 2.7 MiB)
Info::
Third-party blocking time is low (0 ms)
98%
First-party Third-party
D
Page Weight Inventory
Action
63 resources · 2.7 MB · 62 KB savings available
FIX
63 resources · 2.7 MB · 62 KB savings available
Warning::
Page weight 1.7 MB over 1MB target
Got: 2.7 MB Expected: ≤ 1 MB
Info::
~62 KB of savings available
Warning::
62 third-party resources (98% of weight)
Info::
2 resources over 200KB
63 resources · 2.7 MiB · 62 third-party 1.7 MiB over 1MB target
Image 71% · 1.9 MiB
CSS 12% · 323.7 KiB
Font 11% · 306.1 KiB
JavaScript 4% · 117.0 KiB
Document 2% · 59.3 KiB

~62.0 KiB of savings available

Remove unused JavaScript: 62.0 KiB
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.

C
Image Optimization
Action
46 images, 0 KB saveable
REVIEW
46 images, 0 KB saveable
Warning::
https://www.centos.org/assets/img/centos-whitelogo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.centos.org/assets/img/centos-symbol.sv... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.centos.org/assets/img/sponsors/altusho... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://img.youtube.com/vi/ayMpLYBOViQ/hqdefault.j... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://img.youtube.com/vi/neWBY0KwW_Y/hqdefault.j... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://img.youtube.com/vi/-osWEQVvedg/hqdefault.j... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
46 images 1.9 MB
0 oversized -0 KB
45 legacy format
6 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

B
JS Bundles
4 scripts, 62 KB unused
REVIEW
4 scripts, 62 KB unused
Warning::
https://www.centos.org/assets/js/bootstrap.bundle....: 62 KB unused (79%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 62 KB
62 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.centos.org/assets/js/bootstrap.bundle.min.js79 KB62 KB (79%)✓3rd
https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/highlight.min.js35 KB—✓3rd
https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.js1 KB—✓3rd
https://unpkg.com/vanilla-back-to-top@7.2.1/dist/vanilla-back-to-top.min.js2 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+
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
185ms total JS execution
PASS
185ms total JS execution
Info::
https://centos.org/: 95ms CPU time
Info::
Unattributable: 90ms CPU time
Info::
Third-party scripts: 90ms (48% of total)

Main Thread Breakdown

Other 43% Style & Layout 29% Script Evaluation 14% Parse HTML & CSS 6% Rendering 6%
ScriptTotalScriptingParse/CompileParty
https://centos.org/95ms7ms1ms1st
Unattributable90ms2ms0ms3rd
A+
Font Loading
3 fonts (306 KB)
PASS
3 fonts (306 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

306 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 1.0 s 2.0 s 3.0 s FCP 1.1 s LCP 3.0 shttps://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.1/webfonts/fa-solid-900.woff2fa-solid-900.woff2 https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.1/webfonts/fa-solid-900.woff2 — 155.0 KiB — 69 ms — font-display: swaphttps://fonts.gstatic.com/s/montserrat/v31/JTUSjIg1_i6t8kCHKm459WlhyyTh89Y.woff2JTUSjIg1_i6t8kCHKm459Wl... https://fonts.gstatic.com/s/montserrat/v31/JTUSjIg1_i6t8kCHKm459WlhyyTh89Y.woff2 — 34.7 KiB — 34 ms — font-display: swaphttps://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.1/webfonts/fa-brands-400.woff2fa-brands-400.woff2 https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.1/webfonts/fa-brands-400.woff2 — 116.4 KiB — 82 ms — font-display: swap
fa-solid-900.woff2 woff2 swap
Size 155 KB
Load time 69 ms
Start 389 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
JTUSjIg1_i6t8kCHKm459Wl... woff2 swap
Size 35 KB
Load time 34 ms
Start 390 ms
Risk FOUT — text flashes from fallback to web font
fa-brands-400.woff2 woff2 swap
Size 116 KB
Load time 82 ms
Start 390 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
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 ~136 KB and ~272 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
Network Waterfall
63 requests over 672ms
INFO
0 ms 1.0 s 2.0 s 3.0 s FCP 1.1 s LCP 3.0 shttps://centos.org// https://centos.org/ — 200 — 42.0 KiB — 155 ms — http/1.1https://fonts.googleapis.com/css2?family=Montserrat:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&family=Source+Code+Pro:ital,wght@0,400;0,500;0,700;1,400;1,500;1,700&display=swapfonts.googleapis.com/css2?family=Mo... https://fonts.googleapis.com/css2?family=Montserrat:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&family=Source+Code+Pro:ital,wght@0,400;0,500;0,700;1,400;1,500;1,700&display=swap — 200 — 1.6 KiB — 82 ms — h2https://fonts.googleapis.com/css2?family=Source+Code+Pro:ital,wght@0,400;0,500;0,700;1,400;1,500;1,700&display=swapfonts.googleapis.com/css2?family=So... https://fonts.googleapis.com/css2?family=Source+Code+Pro:ital,wght@0,400;0,500;0,700;1,400;1,500;1,700&display=swap — 200 — 1.3 KiB — 80 ms — h2https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.1/css/all.min.csscdnjs.cloudflare.com/ajax/libs/font... https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.1/css/all.min.css — 200 — 22.6 KiB — 76 ms — h2https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/styles/stackoverflow-light.min.csscdnjs.cloudflare.com/ajax/libs/high... https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/styles/stackoverflow-light.min.css — 200 — 1.1 KiB — 72 ms — h2https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.cssunpkg.com/highlightjs-copy@1.0.3/di... https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.css — 200 — 1.3 KiB — 63 ms — h3https://www.centos.org/assets/css/base/stylesheet.min.csswww.centos.org/assets/css/base/styl... https://www.centos.org/assets/css/base/stylesheet.min.css — 200 — 295.7 KiB — 219 ms — http/1.1https://www.centos.org/assets/img/centos-whitelogo.svgwww.centos.org/assets/img/centos-wh... https://www.centos.org/assets/img/centos-whitelogo.svg — 200 — 4.0 KiB — 101 ms — http/1.1https://www.centos.org/assets/img/centos-symbol.svgwww.centos.org/assets/img/centos-sy... https://www.centos.org/assets/img/centos-symbol.svg — 200 — 2.1 KiB — 100 ms — http/1.1https://www.centos.org/site.webmanifestwww.centos.org/site.webmanifest https://www.centos.org/site.webmanifest — 404 — 8.6 KiB — 99 ms — http/1.1https://img.youtube.com/vi/neWBY0KwW_Y/hqdefault.jpgimg.youtube.com/vi/neWBY0KwW_Y/hqde... https://img.youtube.com/vi/neWBY0KwW_Y/hqdefault.jpg — 200 — 19.2 KiB — 87 ms — h2https://img.youtube.com/vi/-osWEQVvedg/hqdefault.jpgimg.youtube.com/vi/-osWEQVvedg/hqde... https://img.youtube.com/vi/-osWEQVvedg/hqdefault.jpg — 200 — 17.0 KiB — 105 ms — h2https://img.youtube.com/vi/ayMpLYBOViQ/hqdefault.jpgimg.youtube.com/vi/ayMpLYBOViQ/hqde... https://img.youtube.com/vi/ayMpLYBOViQ/hqdefault.jpg — 200 — 17.6 KiB — 113 ms — h2https://www.centos.org/assets/img/sponsors/altushost.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/altushost.png — 200 — 6.1 KiB — 96 ms — http/1.1https://www.centos.org/assets/img/sponsors/am-logo.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/am-logo.png — 200 — 6.3 KiB — 95 ms — http/1.1https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/highlight.min.jscdnjs.cloudflare.com/ajax/libs/high... https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/highlight.min.js — 200 — 35.2 KiB — 29 ms — h2https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.jsunpkg.com/highlightjs-copy@1.0.3/di... https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.js — 200 — 950 B — 38 ms — h3https://unpkg.com/vanilla-back-to-top@7.2.1/dist/vanilla-back-to-top.min.jsunpkg.com/vanilla-back-to-top@7.2.1... https://unpkg.com/vanilla-back-to-top@7.2.1/dist/vanilla-back-to-top.min.js — 200 — 1.6 KiB — 36 ms — h3https://www.centos.org/assets/js/bootstrap.bundle.min.jswww.centos.org/assets/js/bootstrap.... https://www.centos.org/assets/js/bootstrap.bundle.min.js — 200 — 79.3 KiB — 93 ms — http/1.1https://www.centos.org/assets/img/sponsors/aws.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/aws.png — 200 — 4.9 KiB — 34 ms — http/1.1https://www.centos.org/assets/img/sponsors/baseip_240x60.jpgwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/baseip_240x60.jpg — 200 — 8.0 KiB — 44 ms — http/1.1https://www.centos.org/assets/img/sponsors/binaryracks.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/binaryracks.png — 200 — 4.3 KiB — 33 ms — http/1.1https://www.centos.org/assets/img/sponsors/cdn77.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/cdn77.png — 200 — 9.6 KiB — 48 ms — http/1.1https://www.centos.org/assets/img/sponsors/clientvps.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/clientvps.png — 200 — 1.4 KiB — 51 ms — http/1.1https://www.centos.org/assets/img/sponsors/colocation-america.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/colocation-america.png — 200 — 10.5 KiB — 34 ms — http/1.1https://www.centos.org/assets/img/sponsors/dedicatedsolutions.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/dedicatedsolutions.png — 200 — 4.4 KiB — 47 ms — http/1.1https://www.centos.org/assets/img/sponsors/eukhost.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/eukhost.png — 200 — 15.2 KiB — 63 ms — http/1.1https://www.centos.org/assets/img/sponsors/fasthosts.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/fasthosts.png — 200 — 5.7 KiB — 34 ms — http/1.1https://www.centos.org/assets/img/sponsors/GameHost.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/GameHost.png — 200 — 6.8 KiB — 34 ms — http/1.1https://www.centos.org/assets/img/sponsors/hostiserver.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/hostiserver.png — 200 — 11.2 KiB — 33 ms — http/1.1
0 ms 1.0 s 2.0 s 3.0 s FCP 1.1 s LCP 3.0 shttps://centos.org// https://centos.org/ — 200 — 42.0 KiB — 155 ms — http/1.1https://fonts.googleapis.com/css2?family=Montserrat:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&family=Source+Code+Pro:ital,wght@0,400;0,500;0,700;1,400;1,500;1,700&display=swapfonts.googleapis.com/css2?family=Mo... https://fonts.googleapis.com/css2?family=Montserrat:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&family=Source+Code+Pro:ital,wght@0,400;0,500;0,700;1,400;1,500;1,700&display=swap — 200 — 1.6 KiB — 82 ms — h2https://fonts.googleapis.com/css2?family=Source+Code+Pro:ital,wght@0,400;0,500;0,700;1,400;1,500;1,700&display=swapfonts.googleapis.com/css2?family=So... https://fonts.googleapis.com/css2?family=Source+Code+Pro:ital,wght@0,400;0,500;0,700;1,400;1,500;1,700&display=swap — 200 — 1.3 KiB — 80 ms — h2https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.1/css/all.min.csscdnjs.cloudflare.com/ajax/libs/font... https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.1/css/all.min.css — 200 — 22.6 KiB — 76 ms — h2https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/styles/stackoverflow-light.min.csscdnjs.cloudflare.com/ajax/libs/high... https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/styles/stackoverflow-light.min.css — 200 — 1.1 KiB — 72 ms — h2https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.cssunpkg.com/highlightjs-copy@1.0.3/di... https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.css — 200 — 1.3 KiB — 63 ms — h3https://www.centos.org/assets/css/base/stylesheet.min.csswww.centos.org/assets/css/base/styl... https://www.centos.org/assets/css/base/stylesheet.min.css — 200 — 295.7 KiB — 219 ms — http/1.1https://www.centos.org/assets/img/centos-whitelogo.svgwww.centos.org/assets/img/centos-wh... https://www.centos.org/assets/img/centos-whitelogo.svg — 200 — 4.0 KiB — 101 ms — http/1.1https://www.centos.org/assets/img/centos-symbol.svgwww.centos.org/assets/img/centos-sy... https://www.centos.org/assets/img/centos-symbol.svg — 200 — 2.1 KiB — 100 ms — http/1.1https://www.centos.org/site.webmanifestwww.centos.org/site.webmanifest https://www.centos.org/site.webmanifest — 404 — 8.6 KiB — 99 ms — http/1.1https://img.youtube.com/vi/neWBY0KwW_Y/hqdefault.jpgimg.youtube.com/vi/neWBY0KwW_Y/hqde... https://img.youtube.com/vi/neWBY0KwW_Y/hqdefault.jpg — 200 — 19.2 KiB — 87 ms — h2https://img.youtube.com/vi/-osWEQVvedg/hqdefault.jpgimg.youtube.com/vi/-osWEQVvedg/hqde... https://img.youtube.com/vi/-osWEQVvedg/hqdefault.jpg — 200 — 17.0 KiB — 105 ms — h2https://img.youtube.com/vi/ayMpLYBOViQ/hqdefault.jpgimg.youtube.com/vi/ayMpLYBOViQ/hqde... https://img.youtube.com/vi/ayMpLYBOViQ/hqdefault.jpg — 200 — 17.6 KiB — 113 ms — h2https://www.centos.org/assets/img/sponsors/altushost.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/altushost.png — 200 — 6.1 KiB — 96 ms — http/1.1https://www.centos.org/assets/img/sponsors/am-logo.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/am-logo.png — 200 — 6.3 KiB — 95 ms — http/1.1https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/highlight.min.jscdnjs.cloudflare.com/ajax/libs/high... https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.7.0/highlight.min.js — 200 — 35.2 KiB — 29 ms — h2https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.jsunpkg.com/highlightjs-copy@1.0.3/di... https://unpkg.com/highlightjs-copy@1.0.3/dist/highlightjs-copy.min.js — 200 — 950 B — 38 ms — h3https://unpkg.com/vanilla-back-to-top@7.2.1/dist/vanilla-back-to-top.min.jsunpkg.com/vanilla-back-to-top@7.2.1... https://unpkg.com/vanilla-back-to-top@7.2.1/dist/vanilla-back-to-top.min.js — 200 — 1.6 KiB — 36 ms — h3https://www.centos.org/assets/js/bootstrap.bundle.min.jswww.centos.org/assets/js/bootstrap.... https://www.centos.org/assets/js/bootstrap.bundle.min.js — 200 — 79.3 KiB — 93 ms — http/1.1https://www.centos.org/assets/img/sponsors/aws.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/aws.png — 200 — 4.9 KiB — 34 ms — http/1.1https://www.centos.org/assets/img/sponsors/baseip_240x60.jpgwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/baseip_240x60.jpg — 200 — 8.0 KiB — 44 ms — http/1.1https://www.centos.org/assets/img/sponsors/binaryracks.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/binaryracks.png — 200 — 4.3 KiB — 33 ms — http/1.1https://www.centos.org/assets/img/sponsors/cdn77.pngwww.centos.org/assets/img/sponsors/... https://www.centos.org/assets/img/sponsors/cdn77.png — 200 — 9.6 KiB — 48 ms — 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HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
48% of JavaScript execution is third-party
First-party Third-party 90ms · 0KB · €1/mo
Unattributable
Other
Optional
Execution 90ms
Transfer 0 KB
Monthly Cost €1/mo

48% 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

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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