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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
73
GRADE
C
FIX
2
REVIEW
4
PASS
6
INFO
2

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

Mobile Desktop
83
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
93
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
77
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.

604 ms

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

2.26 s

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

131 ms

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

0.108

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

712 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.

2.55 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
14
6 PASS 4 REVIEW 2 FIX
F
Page Weight Budget
Action
3.5 MB transferred, 110 requests
FIX
3.5 MB transferred, 110 requests
Warning::
Page weighs 5.8 MB (3.5 MB transferred)
Warning::
Images are 2.2 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 2.2 MB
Warning::
JavaScript is 753 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 753 KB
Warning::
110 HTTP requests — consider bundling or reducing
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Info::
Estimated 0.73 g CO2 per page load
3.5 MB / 2.4 MB budget
3.5 MB transferred
110 requests
0.73 g CO2 per page load
Images 2.2 MiB 62%
JavaScript 753.1 KiB 21%
HTML 299.9 KiB 8%
Fonts 165.0 KiB 5%
Other 97.5 KiB 3%
CSS 31.7 KiB 1%
Other 1.5 KiB 0%
Other 701 B 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

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

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Why this matters

High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.

Source: web.dev

D
JS Bundles
Action
49 scripts, 160 KB unused
FIX
49 scripts, 160 KB unused
Warning::
https://www.googletagmanager.com/gtag/js?id=G-58L1...: 62 KB unused (44%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://ajax.googleapis.com/ajax/libs/jquery/1.11....: 51 KB unused (62%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://ajax.googleapis.com/ajax/libs/jquery/1.11....: unminified — 39 KB could be saved
Warning::
https://reactnative.dev/assets/js/main.f6a6aa6b.js: 47 KB unused (20%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 160 KB
160 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtag/js?id=G-58L13S6BDP142 KB62 KB (44%)✓3rd
https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.js83 KB51 KB (62%)✗3rd
https://reactnative.dev/assets/js/main.f6a6aa6b.js243 KB47 KB (20%)✓1st
https://reactnative.dev/assets/js/36994c47.2c442902.js0 KB—✓1st
https://reactnative.dev/assets/js/17896441.4a32d8e5.js3 KB—✓1st
https://reactnative.dev/assets/js/runtime~main.6b89969c.js47 KB—✓1st
https://snack.expo.dev/embed.js2 KB—✓3rd
https://widget.surveymonkey.com/collect/website/js/tRaiETqnLgj758hTBazgd8ryO5qrZo8Exadq9qmt1wtm4_2FdZGEAKHDFEt_2BBlwwM4.js16 KB—✗3rd
https://widget.surveymonkey.com/collect/website/js/cookie.js?_=17753281517740 KB—✓3rd
https://reactnative.dev/assets/js/77353.6aaf2945.js2 KB—✓1st

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

C
Image Optimization
Action
46 images, 0 KB saveable
REVIEW
46 images, 0 KB saveable
Warning::
https://reactnative.dev/img/showcase/mercari.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/nfl.webp is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/teamsmobile.p... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/shopify.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/shop.webp is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/puma.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/mattermost.we... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/homepage/libraries.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/officemobile.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/amazon-shoppi... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/coinbase.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/discord.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/bloomberg.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/tesla.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/homepage/file-based-ro... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/outlookmobile... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/homepage/tools.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/facebook.webp is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/playstation.p... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/wordpress.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/klarna.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/homepage/devices.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/adsmanager.pn... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/tableau.webp is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/bolt.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/header_logo.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/messengerdesk... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/flipkart.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/oss_logo.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/homepage/dissection.pn... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/metahorizon.w... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://reactnative.dev/img/showcase/xboxgamepass.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
46 images 2.2 MB
0 oversized -0 KB
37 legacy format
32 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

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

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

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

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

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

C
JS Execution Cost
Action
1133ms total JS execution
REVIEW
1133ms total JS execution
Warning::
https://reactnative.dev/assets/js/main.f6a6aa6b.js: 400ms CPU time
Warning::
https://reactnative.dev/: 327ms CPU time
Info::
Unattributable: 213ms CPU time
Info::
https://www.googletagmanager.com/gtag/js?id=G-58L1...: 124ms CPU time
Info::
https://platform.twitter.com/widgets.js: 68ms CPU time
Info::
Third-party scripts: 406ms (36% of total)

Main Thread Breakdown

Script Evaluation 44% Other 21% Style & Layout 19% Script Parsing & Compilation 9%
ScriptTotalScriptingParse/CompileParty
https://reactnative.dev/assets/js/main.f6a6aa6b.js400ms306ms64ms1st
https://reactnative.dev/327ms23ms3ms1st
Unattributable213ms3ms0ms3rd
https://www.googletagmanager.com/gtag/js?id=G-58L13S6BDP124ms107ms16ms3rd
https://platform.twitter.com/widgets.js68ms52ms4ms3rd
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::
ETag present — enables conditional (304) responses
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+
Third-Party Impact
19% third-party, 0 ms blocking
PASS
19% third-party, 0 ms blocking
Info::
Third-party code accounts for 19% of page weight (697.5 KiB of 3.5 MiB)
Info::
Third-party blocking time is low (0 ms)
81%
19%
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 (165 KB)
PASS
5 fonts (165 KB)
Info::
5 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

5

165 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 500 ms 1.0 s 1.5 s 2.0 s FCP 604 ms LCP 2.3 shttps://reactnative.dev/assets/fonts/Optimistic-Display-Light-199be98cf48e5b4c688356b08a02362c.woff2Optimistic-Display-Ligh... https://reactnative.dev/assets/fonts/Optimistic-Display-Light-199be98cf48e5b4c688356b08a02362c.woff2 — 21.8 KiB — 0 ms — font-display: swaphttps://reactnative.dev/assets/fonts/Optimistic-Display-Bold-cac0444e353f65c7263980c51631096a.woff2Optimistic-Display-Bold... https://reactnative.dev/assets/fonts/Optimistic-Display-Bold-cac0444e353f65c7263980c51631096a.woff2 — 23.2 KiB — 0 ms — font-display: swaphttps://reactnative.dev/assets/fonts/Optimistic-Display-Medium-0670086c0b69b506967af1cab0ed1f22.woff2Optimistic-Display-Medi... https://reactnative.dev/assets/fonts/Optimistic-Display-Medium-0670086c0b69b506967af1cab0ed1f22.woff2 — 22.9 KiB — 0 ms — font-display: swaphttps://reactnative.dev/assets/fonts/Optimistic-Display-Regular-b0e4e99f91efd0021c3ab8e4df0e6e1b.woff2Optimistic-Display-Regu... https://reactnative.dev/assets/fonts/Optimistic-Display-Regular-b0e4e99f91efd0021c3ab8e4df0e6e1b.woff2 — 22.4 KiB — 0 ms — font-display: swaphttps://reactnative.dev/assets/fonts/Source-Code-Pro-Regular-a7968a8070a7b4cfb4050a96e1eea6eb.woff2Source-Code-Pro-Regular... https://reactnative.dev/assets/fonts/Source-Code-Pro-Regular-a7968a8070a7b4cfb4050a96e1eea6eb.woff2 — 74.7 KiB — 0 ms — font-display: swap
Optimistic-Display-Ligh... woff2 swap
Size 22 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Optimistic-Display-Bold... woff2 swap
Size 23 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Optimistic-Display-Medi... woff2 swap
Size 23 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Optimistic-Display-Regu... woff2 swap
Size 22 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Source-Code-Pro-Regular... woff2 swap
Size 75 KB
Load time 0 ms
Start 0 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
110 requests over 0ms
INFO

Performance analysis not available for this result.

Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
36% of JavaScript execution is third-party
First-party Third-party 406ms · 170KB · €4/mo
Unattributable
Other
Costly
Execution 213ms
Transfer 0 KB
Monthly Cost €2/mo
Google Tag Manager
Tag Manager
Optional
Execution 124ms
Transfer 142 KB
Unused 44%
Monthly Cost €1/mo
Twitter/X Embed
Social
Optional
Execution 68ms
Transfer 27 KB
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • Unattributable adds 213ms and costs ~€2/month

Unattributable takes 213ms 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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