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https://dev.to

Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
80
GRADE
B
FIX
3
REVIEW
4
PASS
7
INFO
2

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

Mobile Desktop
55
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
81
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.

7.32 s

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

16.70 s

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

200 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.

7.32 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.

16.86 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
16
7 PASS 4 REVIEW 3 FIX
F
Page Weight Budget
Action
2.6 MB transferred, 74 requests
FIX
2.6 MB transferred, 74 requests
Warning::
Page weighs 7.3 MB (2.6 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
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::
74 HTTP requests
Info::
Estimated 0.54 g CO2 per page load
2.6 MB / 2.4 MB budget
2.6 MB transferred
74 requests
0.54 g CO2 per page load
JavaScript 1.4 MiB 55%
Images 826.3 KiB 31%
CSS 208.2 KiB 8%
HTML 104.3 KiB 4%
Fonts 33.9 KiB 1%
Other 9.6 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

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 (2.5 MiB of 2.6 MiB)
Info::
Third-party blocking time is low (0 ms)
98%
First-party Third-party
D
JS Bundles
Action
22 scripts, 407 KB unused
FIX
22 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 (41%)
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 (41%)✓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
29 images, 0 KB saveable
REVIEW
29 images, 0 KB saveable
Info::
All images are well-optimized
29 images 826 KB
0 oversized -0 KB
8 legacy format
0 missing dimensions CLS risk
C
JS Execution Cost
Action
1380ms total JS execution
REVIEW
1380ms total JS execution
Warning::
Unattributable: 348ms CPU time
Warning::
https://assets.dev.to/assets/base-0c748bbcdc300412...: 324ms CPU time
Info::
https://dev.to/: 243ms CPU time
Info::
https://www.googletagmanager.com/gtag/js?id=G-TYEM...: 202ms CPU time
Info::
https://assets.dev.to/assets/homePage-fd5d5a8d3dab...: 116ms CPU time
Warning::
Third-party scripts: 1137ms (82% of total)

Main Thread Breakdown

Script Evaluation 35% Other 26% Style & Layout 15% Script Parsing & Compilation 12% Parse HTML & CSS 8% Rendering 5%
ScriptTotalScriptingParse/CompileParty
Unattributable348ms10ms0ms3rd
https://assets.dev.to/assets/base-0c748bbcdc30041261c326ef2ce931fbce46c58bc3c488da881ae35c4750941d.js324ms100ms16ms3rd
https://dev.to/243ms20ms2ms1st
https://www.googletagmanager.com/gtag/js?id=G-TYEM8Y3JN3202ms153ms48ms3rd
https://assets.dev.to/assets/homePage-fd5d5a8d3dabded9230df005c7df04e1ea5e6dd70b8171bd952cf1e48a146c41.js116ms73ms42ms3rd
https://assets.dev.to/assets/baseTracking-b6bf73e5ee66633e151e7d5b7c6bbccedfa4c59e3615be97b98c4c0f543ddae7.js89ms86ms1ms3rd
https://assets.dev.to/assets/application-0b268684912bef9b0f23defff01cb608bfc5d5e5610287725e7b686139ae32d3.js59ms13ms45ms3rd
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+
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 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s 14.0 s 16.0 s FCP 7.3 s LCP 16.7 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
A+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
No render-blocking resources detected in <head>
A+
Third-Party Resources
No third-party resources detected
PASS
No third-party resources detected
Network Waterfall
74 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
82% of JavaScript execution is third-party
First-party Third-party 1137ms · 565KB · €12/mo
Unattributable
Other
Costly
Execution 348ms
Transfer 0 KB
Monthly Cost €4/mo
assets.dev.to
Other
Costly
Execution 324ms
Transfer 50 KB
Unused 71%
Monthly Cost €4/mo
Google Tag Manager
Tag Manager
Costly
Execution 202ms
Transfer 152 KB
Unused 41%
Monthly Cost €2/mo
assets.dev.to
Other
Optional
Execution 116ms
Transfer 169 KB
Unused 74%
Monthly Cost €1/mo
assets.dev.to
Other
Optional
Execution 89ms
Transfer 3 KB
Monthly Cost €1/mo
assets.dev.to
Other
Optional
Execution 59ms
Transfer 191 KB
Unused 98%
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • Unattributable adds 348ms and costs ~€4/month
  • assets.dev.to adds 324ms and costs ~€4/month
  • Google Tag Manager adds 202ms and costs ~€2/month

82% 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

Unattributable takes 348ms 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

assets.dev.to takes 324ms 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

71% of assets.dev.to'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

Google Tag Manager takes 202ms 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

74% of assets.dev.to'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

98% of assets.dev.to'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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