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Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
85
GRADE
B
FIX
1
REVIEW
6
PASS
6
INFO
2

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

Mobile Desktop
98
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
95
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.
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.

587 ms

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

1.03 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.

0.000

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

715 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.

1.03 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 6 REVIEW 1 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 (1.1 MiB of 1.1 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
B
Page Weight Budget
1.1 MB transferred, 69 requests
REVIEW
1.1 MB transferred, 69 requests
Info::
Page weighs 2.5 MB (1.1 MB transferred)
Warning::
JavaScript is 543 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 543 KB
Info::
Fonts are 314 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 314 KB
Info::
69 HTTP requests
Info::
Estimated 0.23 g CO2 per page load
1.1 MB / 2.4 MB budget
1.1 MB transferred
69 requests
0.23 g CO2 per page load
JavaScript 542.5 KiB 49%
Fonts 314.2 KiB 28%
Images 161.3 KiB 15%
HTML 42.8 KiB 4%
Other 21.7 KiB 2%
CSS 20.1 KiB 2%
Other 2.0 KiB 0%
Other 750 B 0%
0 2.4 MB 4.9 MB
Under budget

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Why this matters

JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.

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

B
Image Optimization
34 images, 0 KB saveable
REVIEW
34 images, 0 KB saveable
Info::
All images are well-optimized
34 images 161 KB
0 oversized -0 KB
31 legacy format
0 missing dimensions CLS risk
C
JS Bundles
Action
13 scripts, 209 KB unused
REVIEW
13 scripts, 209 KB unused
Warning::
https://www.googletagmanager.com/gtag/js?id=G-B1E8...: 63 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://react.dev/_next/static/chunks/4ad82c5e.aa0...: 45 KB unused (90%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://react.dev/_next/static/chunks/811.b2e5ca62...: 44 KB unused (40%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://react.dev/_next/static/chunks/928-e89de0bd...: 32 KB unused (34%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://react.dev/_next/static/chunks/668-9be9de6f...: 26 KB unused (76%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 209 KB
209 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtag/js?id=G-B1E83PJ3RT146 KB63 KB (43%)✓3rd
https://react.dev/_next/static/chunks/4ad82c5e.aa059996e264f809.js50 KB45 KB (90%)✓3rd
https://react.dev/_next/static/chunks/811.b2e5ca620a3f883e.js110 KB44 KB (40%)✓3rd
https://react.dev/_next/static/chunks/928-e89de0bd2e20fa8c.js94 KB32 KB (34%)✓3rd
https://react.dev/_next/static/chunks/668-9be9de6fa7660277.js34 KB26 KB (76%)✓3rd
https://react.dev/_next/static/chunks/main-8bc660a98b463b2d.js39 KB—✓3rd
https://react.dev/_next/static/chunks/pages/_app-6d7b64b3b21a9551.js1 KB—✓3rd
https://react.dev/_next/static/chunks/pages/%5B%5B...markdownPath%5D%5D-ef91ae665155f68d.js3 KB—✓3rd
https://react.dev/_next/static/MNWyTLE_bcVMjrXmgoiBA/_buildManifest.js1 KB—✓3rd
https://react.dev/_next/static/MNWyTLE_bcVMjrXmgoiBA/_ssgManifest.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

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

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

B
Page Weight Inventory
69 resources · 1.1 MB · 209 KB savings available
REVIEW
69 resources · 1.1 MB · 209 KB savings available
Warning::
Page weight 81 KB over 1MB target
Got: 1.1 MB Expected: ≤ 1 MB
Info::
~209 KB of savings available
Warning::
68 third-party resources (100% of weight)
69 resources · 1.1 MiB · 68 third-party 81.3 KiB over 1MB target
JavaScript 49% · 542.5 KiB
Font 28% · 314.2 KiB
Image 15% · 163.2 KiB
Document 4% · 43.0 KiB
Other 2% · 22.4 KiB
CSS 2% · 20.1 KiB

~209.4 KiB of savings available

Remove unused JavaScript: 209.4 KiB
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

B
HTTP Caching
public, max-age=0, must-revalidate
REVIEW
public, max-age=0, must-revalidate
Info::
Cache-Control header is set
Got: public, max-age=0, must-revalidate
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

public, max-age=0, must-revalidate

DirectiveValueMeaning
public—Any cache may store this response
max-age0Cache for 0 seconds
must-revalidate—Must recheck with server after expiry
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
390ms total JS execution
PASS
390ms total JS execution
Info::
https://react.dev/: 125ms CPU time
Info::
https://react.dev/_next/static/chunks/framework-76...: 125ms CPU time
Info::
Unattributable: 83ms CPU time
Info::
https://www.googletagmanager.com/gtag/js?id=G-B1E8...: 57ms CPU time
Warning::
Third-party scripts: 390ms (100% of total)

Main Thread Breakdown

Script Evaluation 49% Style & Layout 20% Other 18% Script Parsing & Compilation 7%
ScriptTotalScriptingParse/CompileParty
https://react.dev/125ms6ms1ms3rd
https://react.dev/_next/static/chunks/framework-76ad44d61c11f057.js125ms112ms3ms3rd
Unattributable83ms3ms0ms3rd
https://www.googletagmanager.com/gtag/js?id=G-B1E83PJ3RT57ms48ms9ms3rd
A+
Font Loading
9 fonts (314 KB)
PASS
9 fonts (314 KB)
Info::
9 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

9

314 KB total

Render-blocking

0

of 9

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s FCP 587 ms LCP 1.0 shttps://react.dev/fonts/Source-Code-Pro-Regular.woff2Source-Code-Pro-Regular... https://react.dev/fonts/Source-Code-Pro-Regular.woff2 — 74.8 KiB — 64 ms — font-display: swaphttps://react.dev/fonts/Source-Code-Pro-Bold.woff2Source-Code-Pro-Bold.woff2 https://react.dev/fonts/Source-Code-Pro-Bold.woff2 — 75.8 KiB — 49 ms — font-display: swaphttps://react.dev/fonts/Optimistic_Display_W_Md.woff2Optimistic_Display_W_Md... https://react.dev/fonts/Optimistic_Display_W_Md.woff2 — 23.1 KiB — 57 ms — font-display: swaphttps://react.dev/fonts/Optimistic_Display_W_SBd.woff2Optimistic_Display_W_SB... https://react.dev/fonts/Optimistic_Display_W_SBd.woff2 — 23.3 KiB — 37 ms — font-display: swaphttps://react.dev/fonts/Optimistic_Display_W_Bd.woff2Optimistic_Display_W_Bd... https://react.dev/fonts/Optimistic_Display_W_Bd.woff2 — 23.3 KiB — 54 ms — font-display: swaphttps://react.dev/fonts/Optimistic_Text_W_Md.woff2Optimistic_Text_W_Md.woff2 https://react.dev/fonts/Optimistic_Text_W_Md.woff2 — 23.1 KiB — 53 ms — font-display: swaphttps://react.dev/fonts/Optimistic_Text_W_Bd.woff2Optimistic_Text_W_Bd.woff2 https://react.dev/fonts/Optimistic_Text_W_Bd.woff2 — 23.2 KiB — 34 ms — font-display: swaphttps://react.dev/fonts/Optimistic_Text_W_Rg.woff2Optimistic_Text_W_Rg.woff2 https://react.dev/fonts/Optimistic_Text_W_Rg.woff2 — 22.3 KiB — 61 ms — font-display: swaphttps://react.dev/fonts/Optimistic_Text_W_It.woff2Optimistic_Text_W_It.woff2 https://react.dev/fonts/Optimistic_Text_W_It.woff2 — 25.3 KiB — 58 ms — font-display: swap
Source-Code-Pro-Regular... woff2 swap
Size 75 KB
Load time 64 ms
Start 170 ms
Risk FOUT — text flashes from fallback to web font
Source-Code-Pro-Bold.woff2 woff2 swap
Size 76 KB
Load time 49 ms
Start 170 ms
Risk FOUT — text flashes from fallback to web font
Optimistic_Display_W_Md... woff2 swap
Size 23 KB
Load time 57 ms
Start 171 ms
Risk FOUT — text flashes from fallback to web font
Optimistic_Display_W_SB... woff2 swap
Size 23 KB
Load time 37 ms
Start 171 ms
Risk FOUT — text flashes from fallback to web font
Optimistic_Display_W_Bd... woff2 swap
Size 23 KB
Load time 54 ms
Start 172 ms
Risk FOUT — text flashes from fallback to web font
Optimistic_Text_W_Md.woff2 woff2 swap
Size 23 KB
Load time 53 ms
Start 172 ms
Risk FOUT — text flashes from fallback to web font
Optimistic_Text_W_Bd.woff2 woff2 swap
Size 23 KB
Load time 34 ms
Start 173 ms
Risk FOUT — text flashes from fallback to web font
Optimistic_Text_W_Rg.woff2 woff2 swap
Size 22 KB
Load time 61 ms
Start 173 ms
Risk FOUT — text flashes from fallback to web font
Optimistic_Text_W_It.woff2 woff2 swap
Size 25 KB
Load time 58 ms
Start 173 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
69 requests over 712ms
INFO
0 ms 500 ms 1.0 s FCP 587 ms LCP 1.0 shttps://reactjs.org// https://reactjs.org/ — 308 — 215 B — 81 ms — h2https://react.dev/react.dev/ https://react.dev/ — 200 — 42.8 KiB — 80 ms — h2https://www.googletagmanager.com/gtag/js?id=G-B1E83PJ3RTwww.googletagmanager.com/gtag/js?id... https://www.googletagmanager.com/gtag/js?id=G-B1E83PJ3RT — 200 — 146.5 KiB — 159 ms — h2https://react.dev/fonts/Source-Code-Pro-Regular.woff2react.dev/fonts/Source-Code-Pro-Reg... https://react.dev/fonts/Source-Code-Pro-Regular.woff2 — 200 — 74.8 KiB — 64 ms — h2https://react.dev/fonts/Source-Code-Pro-Bold.woff2react.dev/fonts/Source-Code-Pro-Bol... https://react.dev/fonts/Source-Code-Pro-Bold.woff2 — 200 — 75.8 KiB — 49 ms — h2https://react.dev/fonts/Optimistic_Display_W_Md.woff2react.dev/fonts/Optimistic_Display_... https://react.dev/fonts/Optimistic_Display_W_Md.woff2 — 200 — 23.1 KiB — 57 ms — h2https://react.dev/fonts/Optimistic_Display_W_SBd.woff2react.dev/fonts/Optimistic_Display_... https://react.dev/fonts/Optimistic_Display_W_SBd.woff2 — 200 — 23.3 KiB — 37 ms — h2https://react.dev/fonts/Optimistic_Display_W_Bd.woff2react.dev/fonts/Optimistic_Display_... https://react.dev/fonts/Optimistic_Display_W_Bd.woff2 — 200 — 23.3 KiB — 54 ms — h2https://react.dev/fonts/Optimistic_Text_W_Md.woff2react.dev/fonts/Optimistic_Text_W_M... https://react.dev/fonts/Optimistic_Text_W_Md.woff2 — 200 — 23.1 KiB — 53 ms — h2https://react.dev/fonts/Optimistic_Text_W_Bd.woff2react.dev/fonts/Optimistic_Text_W_B... https://react.dev/fonts/Optimistic_Text_W_Bd.woff2 — 200 — 23.2 KiB — 34 ms — h2https://react.dev/fonts/Optimistic_Text_W_Rg.woff2react.dev/fonts/Optimistic_Text_W_R... https://react.dev/fonts/Optimistic_Text_W_Rg.woff2 — 200 — 22.3 KiB — 61 ms — h2https://react.dev/fonts/Optimistic_Text_W_It.woff2react.dev/fonts/Optimistic_Text_W_I... https://react.dev/fonts/Optimistic_Text_W_It.woff2 — 200 — 25.3 KiB — 58 ms — h2https://react.dev/_next/static/css/08c63e3f3aafb0fb.cssreact.dev/_next/static/css/08c63e3f... https://react.dev/_next/static/css/08c63e3f3aafb0fb.css — 200 — 20.1 KiB — 31 ms — h2https://react.dev/_next/image?url=%2Fimages%2Fuwu.png&w=384&q=75react.dev/_next/image?url=%2Fimages... https://react.dev/_next/image?url=%2Fimages%2Fuwu.png&w=384&q=75 — 200 — 12.6 KiB — 60 ms — h2https://react.dev/images/home/conf2021/cover.svgreact.dev/images/home/conf2021/cove... https://react.dev/images/home/conf2021/cover.svg — 200 — 727 B — 51 ms — h2https://react.dev/images/home/conf2021/andrew.jpgreact.dev/images/home/conf2021/andr... https://react.dev/images/home/conf2021/andrew.jpg — 200 — 2.2 KiB — 84 ms — h2https://react.dev/images/home/conf2021/lauren.jpgreact.dev/images/home/conf2021/laur... https://react.dev/images/home/conf2021/lauren.jpg — 200 — 5.6 KiB — 45 ms — h2https://react.dev/images/home/conf2021/juan.jpgreact.dev/images/home/conf2021/juan... https://react.dev/images/home/conf2021/juan.jpg — 200 — 1.2 KiB — 41 ms — h2https://react.dev/site.webmanifestreact.dev/site.webmanifest https://react.dev/site.webmanifest — 200 — 750 B — 90 ms — h2https://react.dev/_next/image?url=%2Fimages%2Fuwu.png&w=64&q=75react.dev/_next/image?url=%2Fimages... https://react.dev/_next/image?url=%2Fimages%2Fuwu.png&w=64&q=75 — 200 — 2.0 KiB — 80 ms — h2https://react.dev/_next/static/chunks/webpack-c9ab623dfe839ebe.jsreact.dev/_next/static/chunks/webpa... https://react.dev/_next/static/chunks/webpack-c9ab623dfe839ebe.js — 200 — 2.4 KiB — 44 ms — h2https://react.dev/_next/static/chunks/framework-76ad44d61c11f057.jsreact.dev/_next/static/chunks/frame... https://react.dev/_next/static/chunks/framework-76ad44d61c11f057.js — 200 — 57.3 KiB — 90 ms — h2https://react.dev/_next/static/chunks/main-8bc660a98b463b2d.jsreact.dev/_next/static/chunks/main-... https://react.dev/_next/static/chunks/main-8bc660a98b463b2d.js — 200 — 38.6 KiB — 63 ms — h2https://react.dev/_next/static/chunks/pages/_app-6d7b64b3b21a9551.jsreact.dev/_next/static/chunks/pages... https://react.dev/_next/static/chunks/pages/_app-6d7b64b3b21a9551.js — 200 — 1.0 KiB — 38 ms — h2https://react.dev/_next/static/chunks/668-9be9de6fa7660277.jsreact.dev/_next/static/chunks/668-9... https://react.dev/_next/static/chunks/668-9be9de6fa7660277.js — 200 — 33.9 KiB — 57 ms — h2https://react.dev/_next/static/chunks/928-e89de0bd2e20fa8c.jsreact.dev/_next/static/chunks/928-e... https://react.dev/_next/static/chunks/928-e89de0bd2e20fa8c.js — 200 — 93.9 KiB — 76 ms — h2https://react.dev/_next/static/chunks/pages/%5B%5B...markdownPath%5D%5D-ef91ae665155f68d.jsreact.dev/_next/static/chunks/pages... https://react.dev/_next/static/chunks/pages/%5B%5B...markdownPath%5D%5D-ef91ae665155f68d.js — 200 — 3.5 KiB — 38 ms — h2https://react.dev/_next/static/MNWyTLE_bcVMjrXmgoiBA/_buildManifest.jsreact.dev/_next/static/MNWyTLE_bcVM... https://react.dev/_next/static/MNWyTLE_bcVMjrXmgoiBA/_buildManifest.js — 200 — 803 B — 37 ms — h2https://react.dev/_next/static/MNWyTLE_bcVMjrXmgoiBA/_ssgManifest.jsreact.dev/_next/static/MNWyTLE_bcVM... https://react.dev/_next/static/MNWyTLE_bcVMjrXmgoiBA/_ssgManifest.js — 200 — 406 B — 50 ms — h2https://react.dev/images/uwu.pngreact.dev/images/uwu.png https://react.dev/images/uwu.png — 200 — 54.0 KiB — 56 ms — h2
0 ms 500 ms 1.0 s FCP 587 ms LCP 1.0 shttps://reactjs.org// https://reactjs.org/ — 308 — 215 B — 81 ms — h2https://react.dev/react.dev/ https://react.dev/ — 200 — 42.8 KiB — 80 ms — h2https://www.googletagmanager.com/gtag/js?id=G-B1E83PJ3RTwww.googletagmanager.com/gtag/js?id... https://www.googletagmanager.com/gtag/js?id=G-B1E83PJ3RT — 200 — 146.5 KiB — 159 ms — h2https://react.dev/fonts/Source-Code-Pro-Regular.woff2react.dev/fonts/Source-Code-Pro-Reg... https://react.dev/fonts/Source-Code-Pro-Regular.woff2 — 200 — 74.8 KiB — 64 ms — h2https://react.dev/fonts/Source-Code-Pro-Bold.woff2react.dev/fonts/Source-Code-Pro-Bol... https://react.dev/fonts/Source-Code-Pro-Bold.woff2 — 200 — 75.8 KiB — 49 ms — h2https://react.dev/fonts/Optimistic_Display_W_Md.woff2react.dev/fonts/Optimistic_Display_... https://react.dev/fonts/Optimistic_Display_W_Md.woff2 — 200 — 23.1 KiB — 57 ms — h2https://react.dev/fonts/Optimistic_Display_W_SBd.woff2react.dev/fonts/Optimistic_Display_... https://react.dev/fonts/Optimistic_Display_W_SBd.woff2 — 200 — 23.3 KiB — 37 ms — h2https://react.dev/fonts/Optimistic_Display_W_Bd.woff2react.dev/fonts/Optimistic_Display_... https://react.dev/fonts/Optimistic_Display_W_Bd.woff2 — 200 — 23.3 KiB — 54 ms — h2https://react.dev/fonts/Optimistic_Text_W_Md.woff2react.dev/fonts/Optimistic_Text_W_M... https://react.dev/fonts/Optimistic_Text_W_Md.woff2 — 200 — 23.1 KiB — 53 ms — h2https://react.dev/fonts/Optimistic_Text_W_Bd.woff2react.dev/fonts/Optimistic_Text_W_B... https://react.dev/fonts/Optimistic_Text_W_Bd.woff2 — 200 — 23.2 KiB — 34 ms — h2https://react.dev/fonts/Optimistic_Text_W_Rg.woff2react.dev/fonts/Optimistic_Text_W_R... https://react.dev/fonts/Optimistic_Text_W_Rg.woff2 — 200 — 22.3 KiB — 61 ms — h2https://react.dev/fonts/Optimistic_Text_W_It.woff2react.dev/fonts/Optimistic_Text_W_I... https://react.dev/fonts/Optimistic_Text_W_It.woff2 — 200 — 25.3 KiB — 58 ms — h2https://react.dev/_next/static/css/08c63e3f3aafb0fb.cssreact.dev/_next/static/css/08c63e3f... https://react.dev/_next/static/css/08c63e3f3aafb0fb.css — 200 — 20.1 KiB — 31 ms — h2https://react.dev/_next/image?url=%2Fimages%2Fuwu.png&w=384&q=75react.dev/_next/image?url=%2Fimages... https://react.dev/_next/image?url=%2Fimages%2Fuwu.png&w=384&q=75 — 200 — 12.6 KiB — 60 ms — h2https://react.dev/images/home/conf2021/cover.svgreact.dev/images/home/conf2021/cove... https://react.dev/images/home/conf2021/cover.svg — 200 — 727 B — 51 ms — h2https://react.dev/images/home/conf2021/andrew.jpgreact.dev/images/home/conf2021/andr... https://react.dev/images/home/conf2021/andrew.jpg — 200 — 2.2 KiB — 84 ms — h2https://react.dev/images/home/conf2021/lauren.jpgreact.dev/images/home/conf2021/laur... https://react.dev/images/home/conf2021/lauren.jpg — 200 — 5.6 KiB — 45 ms — h2https://react.dev/images/home/conf2021/juan.jpgreact.dev/images/home/conf2021/juan... https://react.dev/images/home/conf2021/juan.jpg — 200 — 1.2 KiB — 41 ms — h2https://react.dev/site.webmanifestreact.dev/site.webmanifest https://react.dev/site.webmanifest — 200 — 750 B — 90 ms — h2https://react.dev/_next/image?url=%2Fimages%2Fuwu.png&w=64&q=75react.dev/_next/image?url=%2Fimages... https://react.dev/_next/image?url=%2Fimages%2Fuwu.png&w=64&q=75 — 200 — 2.0 KiB — 80 ms — h2https://react.dev/_next/static/chunks/webpack-c9ab623dfe839ebe.jsreact.dev/_next/static/chunks/webpa... https://react.dev/_next/static/chunks/webpack-c9ab623dfe839ebe.js — 200 — 2.4 KiB — 44 ms — h2https://react.dev/_next/static/chunks/framework-76ad44d61c11f057.jsreact.dev/_next/static/chunks/frame... https://react.dev/_next/static/chunks/framework-76ad44d61c11f057.js — 200 — 57.3 KiB — 90 ms — h2https://react.dev/_next/static/chunks/main-8bc660a98b463b2d.jsreact.dev/_next/static/chunks/main-... https://react.dev/_next/static/chunks/main-8bc660a98b463b2d.js — 200 — 38.6 KiB — 63 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
100% of JavaScript execution is third-party
First-party Third-party 390ms · 247KB · €4/mo
react.dev
Other
Optional
Execution 125ms
Transfer 43 KB
Monthly Cost €1/mo
react.dev
Other
Optional
Execution 125ms
Transfer 57 KB
Monthly Cost €1/mo
Unattributable
Other
Optional
Execution 83ms
Transfer 0 KB
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 57ms
Transfer 146 KB
Unused 43%
Monthly Cost €1/mo

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

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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