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Performance

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

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

Mobile Desktop
89
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
78
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.
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.

980 ms

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

2.01 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.

1.08 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.

2.02 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
14
6 PASS 3 REVIEW 3 FIX
F
Page Weight Budget
Action
2.9 MB transferred, 78 requests
FIX
2.9 MB transferred, 78 requests
Warning::
Page weighs 7.6 MB (2.9 MB transferred)
Warning::
JavaScript is 1.4 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.4 MB
Warning::
Images are 1.1 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 1.1 MB
Info::
CSS is 208 KB — consider purging unused styles
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
Got: 208 KB
Info::
78 HTTP requests
Info::
Estimated 0.60 g CO2 per page load
2.9 MB / 2.4 MB budget
2.9 MB transferred
78 requests
0.60 g CO2 per page load
JavaScript 1.4 MiB 50%
Images 1.1 MiB 38%
CSS 208.2 KiB 7%
HTML 103.5 KiB 4%
Fonts 33.9 KiB 1%
Other 10.9 KiB 0%
Other 1.4 KiB 0%
Other 1.2 KiB 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Over 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

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

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 (2.8 MiB of 2.9 MiB)
Info::
Third-party blocking time is low (0 ms)
98%
First-party Third-party
D
JS Bundles
Action
21 scripts, 407 KB unused
FIX
21 scripts, 407 KB unused
Warning::
https://assets.dev.to/assets/application-0b2686849...: 186 KB unused (98%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://assets.dev.to/assets/homePage-fd5d5a8d3dab...: 124 KB unused (74%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-TYEM...: 63 KB unused (42%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://assets.dev.to/assets/base-0c748bbcdc300412...: 35 KB unused (71%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 407 KB
407 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://assets.dev.to/assets/application-0b268684912bef9b0f23defff01cb608bfc5d5e5610287725e7b686139ae32d3.js191 KB186 KB (98%)✓3rd
https://assets.dev.to/assets/homePage-fd5d5a8d3dabded9230df005c7df04e1ea5e6dd70b8171bd952cf1e48a146c41.js169 KB124 KB (74%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-TYEM8Y3JN3152 KB63 KB (42%)✓3rd
https://assets.dev.to/assets/base-0c748bbcdc30041261c326ef2ce931fbce46c58bc3c488da881ae35c4750941d.js50 KB35 KB (71%)✓3rd
https://assets.dev.to/assets/heroBannerClose-08daef9d8f6109d73b3876fb088e26e5a46a047f93d787c38871fdbfbfc56e95.js1 KB—✓3rd
https://assets.dev.to/assets/sidebar-sticky-b50612b4f806438cc3900da6214c342edb7a8b5bfe0adf1c1951915579198329.js2 KB—✓3rd
https://assets.dev.to/assets/billboard-365f8f60fc3506e63bc54cc5b0a2e36f4c11024ff6a30dccd5462467f24b5215.js5 KB—✓3rd
https://assets.dev.to/assets/homePageFeedShortcuts-f7364bc2d6cb139c03e7fe80e32782ba5af34857d2b308e3caa8d902e579a3af.js9 KB—✓3rd
https://assets.dev.to/assets/feedPreviewCards-8d16b0b656456a28c0a290f756cf6e21e19833111c4796f48c631bfea8323d51.js12 KB—✓3rd
https://assets.dev.to/assets/storiesList-b9c50cbd898a3a64258a3a49db1c531651b0a4a11937be35ed4651111802b5b5.js1 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

B
Image Optimization
34 images, 0 KB saveable
REVIEW
34 images, 0 KB saveable
Warning::
https://assets.dev.to/assets/subscription-icon-805... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
34 images 1.1 MB
0 oversized -0 KB
8 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

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

B
HTTP Caching
public, no-cache
REVIEW
public, no-cache
Info::
Cache-Control header is set
Got: public, no-cache
Info::
ETag present — enables conditional (304) responses
Cache-Control

public, no-cache

DirectiveValueMeaning
public—Any cache may store this response
no-cache—Cache but always revalidate first
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
252ms total JS execution
PASS
252ms total JS execution
Info::
https://dev.to/: 164ms CPU time
Info::
Unattributable: 88ms CPU time
Info::
Third-party scripts: 88ms (35% of total)

Main Thread Breakdown

Other 29% Script Evaluation 26% Style & Layout 21% Script Parsing & Compilation 10% Parse HTML & CSS 7% Rendering 5%
ScriptTotalScriptingParse/CompileParty
https://dev.to/164ms6ms1ms1st
Unattributable88ms3ms0ms3rd
A+
Font Loading
1 fonts (34 KB)
PASS
1 fonts (34 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

34 KB total

Render-blocking

0

of 1

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 980 ms LCP 2.0 shttps://fonts.gstatic.com/s/roboto/v48/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2KFO7CnqEu92Fr1ME7kSn66a... https://fonts.gstatic.com/s/roboto/v48/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2 — 33.9 KiB — 0 ms — font-display: swap
KFO7CnqEu92Fr1ME7kSn66a... woff2 swap
Size 34 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
78 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
35% of JavaScript execution is third-party
First-party Third-party 88ms · 0KB · €1/mo
Unattributable
Other
Optional
Execution 88ms
Transfer 0 KB
Monthly Cost €1/mo

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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