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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
73
GRADE
C
FIX
3
REVIEW
3
PASS
6
INFO
2

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

Mobile Desktop
49
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
97
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.

2.03 s

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

6.70 s

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

893 ms

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

0.147

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

2.39 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.

9.84 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 3 REVIEW 3 FIX
F
Page Weight Budget
Action
3.3 MB transferred, 76 requests
FIX
3.3 MB transferred, 76 requests
Warning::
Page weighs 5.7 MB (3.3 MB transferred)
Warning::
Images are 2.0 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 2.0 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
Info::
76 HTTP requests
Info::
Estimated 0.69 g CO2 per page load
3.3 MB / 2.4 MB budget
3.3 MB transferred
76 requests
0.69 g CO2 per page load
Images 2.0 MiB 62%
JavaScript 752.9 KiB 22%
HTML 299.9 KiB 9%
Fonts 165.0 KiB 5%
CSS 31.7 KiB 1%
Other 16.9 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

F
JS Execution Cost
Action
3884ms total JS execution
FIX
3884ms total JS execution
Warning::
https://reactnative.dev/assets/js/main.f6a6aa6b.js: 1279ms CPU time
Warning::
https://reactnative.dev/: 1031ms CPU time
Warning::
Unattributable: 736ms CPU time
Warning::
https://www.googletagmanager.com/gtag/js?id=G-58L1...: 373ms CPU time
Warning::
https://platform.twitter.com/widgets.js: 277ms CPU time
Info::
Third-party scripts: 1521ms (39% of total)

Main Thread Breakdown

Script Evaluation 43% Other 22% Style & Layout 19% Script Parsing & Compilation 11%
ScriptTotalScriptingParse/CompileParty
https://reactnative.dev/assets/js/main.f6a6aa6b.js1279ms968ms173ms1st
https://reactnative.dev/1031ms84ms9ms1st
Unattributable736ms13ms0ms3rd
https://www.googletagmanager.com/gtag/js?id=G-58L13S6BDP373ms268ms101ms3rd
https://platform.twitter.com/widgets.js277ms227ms14ms3rd
https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.js136ms67ms57ms3rd
https://reactnative.dev/assets/js/1df93b7f.a1a1db4e.js53ms1ms51ms1st
D
JS Bundles
Action
16 scripts, 155 KB unused
FIX
16 scripts, 155 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: 43 KB unused (19%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 155 KB
155 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 KB43 KB (19%)✓1st
https://widget.surveymonkey.com/collect/website/js/cookie.js?_=17753281341550 KB—✓3rd
https://platform.twitter.com/widgets.js27 KB—✓3rd
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://cdn.jsdelivr.net/npm/focus-visible@5.2.0/dist/focus-visible.min.js2 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
45 images, 0 KB saveable
REVIEW
45 images, 0 KB saveable
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/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/flipkart.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/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/outlookmobile... 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/facebook.webp 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/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/playstation.p... 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/shopify.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/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/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/xboxgamepass.... 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/shop.webp 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/bolt.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/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/dissection.pn... 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/metahorizon.w... 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/teamsmobile.p... 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/mercari.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.
45 images 2.0 MB
0 oversized -0 KB
36 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
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
21% third-party, 0 ms blocking
PASS
21% third-party, 0 ms blocking
Info::
Third-party code accounts for 21% of page weight (697.3 KiB of 3.3 MiB)
Info::
Third-party blocking time is low (0 ms)
79%
21%
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 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s 6.0 s 7.0 s FCP 2.0 s LCP 6.7 shttps://reactnative.dev/assets/fonts/Optimistic-Display-Regular-b0e4e99f91efd0021c3ab8e4df0e6e1b.woff2Optimistic-Display-Regu... https://reactnative.dev/assets/fonts/Optimistic-Display-Regular-b0e4e99f91efd0021c3ab8e4df0e6e1b.woff2 — 22.5 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-Light-199be98cf48e5b4c688356b08a02362c.woff2Optimistic-Display-Ligh... https://reactnative.dev/assets/fonts/Optimistic-Display-Light-199be98cf48e5b4c688356b08a02362c.woff2 — 21.7 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/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-Regu... 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-Ligh... woff2 swap
Size 22 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
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
46 hints, 0 missing preconnects
PASS
46 hints, 0 missing preconnects
Info::
Page uses 46 resource hint(s)

Current Resource Hints

preconnect
3
preload
+31
41
dns-prefetch
—
prefetch
2

46 resource hints configured

Network Waterfall
76 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
39% of JavaScript execution is third-party
First-party Third-party 1521ms · 253KB · €17/mo
Unattributable
Other
Costly
Execution 736ms
Transfer 0 KB
Monthly Cost €8/mo
Google Tag Manager
Tag Manager
Costly
Execution 373ms
Transfer 142 KB
Unused 44%
Monthly Cost €4/mo
Twitter/X Embed
Social
Costly
Execution 277ms
Transfer 27 KB
Monthly Cost €3/mo
ajax.googleapis.com
Other
Optional
Execution 136ms
Transfer 83 KB
Unused 62%
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • Unattributable adds 736ms and costs ~€8/month
  • Google Tag Manager adds 373ms and costs ~€4/month
  • Twitter/X Embed adds 277ms and costs ~€3/month

Unattributable takes 736ms 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

Google Tag Manager takes 373ms 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

Twitter/X Embed takes 277ms 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

62% of ajax.googleapis.com's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

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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