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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
86
GRADE
B
FIX
2
REVIEW
4
PASS
6
INFO
2

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

Mobile Desktop
96
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
79
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.

880 ms

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

1.31 s

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

19 ms

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

0.008

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

880 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.

1.99 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
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 (1.2 MiB of 1.2 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
No Cache-Control header found
Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

B
Page Weight Budget
1.2 MB transferred, 79 requests
REVIEW
1.2 MB transferred, 79 requests
Info::
Page weighs 3.2 MB (1.2 MB transferred)
Warning::
JavaScript is 563 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 563 KB
Info::
79 HTTP requests
Info::
Estimated 0.26 g CO2 per page load
1.2 MB / 2.4 MB budget
1.2 MB transferred
79 requests
0.26 g CO2 per page load
JavaScript 563.1 KiB 44%
Images 412.0 KiB 32%
Fonts 110.8 KiB 9%
HTML 67.0 KiB 5%
CSS 55.2 KiB 4%
Other 38.1 KiB 3%
Other 18.9 KiB 1%
Other 4.2 KiB 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

B
JS Execution Cost
558ms total JS execution
REVIEW
558ms total JS execution
Warning::
Unattributable: 261ms CPU time
Info::
https://stackoverflow.blog/: 171ms CPU time
Info::
https://cdn.cookielaw.org/scripttemplates/202402.1...: 70ms CPU time
Info::
https://www.googletagmanager.com/gtag/js?id=G-DTTX...: 56ms CPU time
Warning::
Third-party scripts: 558ms (100% of total)

Main Thread Breakdown

Script Evaluation 45% Other 24% Style & Layout 20% Script Parsing & Compilation 4% Rendering 4% Parse HTML & CSS 3%
ScriptTotalScriptingParse/CompileParty
Unattributable261ms143ms0ms3rd
https://stackoverflow.blog/171ms10ms1ms3rd
https://cdn.cookielaw.org/scripttemplates/202402.1.0/otBannerSdk.js70ms43ms9ms3rd
https://www.googletagmanager.com/gtag/js?id=G-DTTX7JCXEJ56ms43ms11ms3rd
B
JS Bundles
22 scripts, 148 KB unused
REVIEW
22 scripts, 148 KB unused
Warning::
https://www.googletagmanager.com/gtag/js?id=G-DTTX...: 63 KB unused (42%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cdn.cookielaw.org/scripttemplates/202402.1...: 56 KB unused (54%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://stackoverflow.blog/_nuxt/DSwynrvu.js: 29 KB unused (36%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 148 KB
148 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtag/js?id=G-DTTX7JCXEJ151 KB63 KB (42%)✓3rd
https://cdn.cookielaw.org/scripttemplates/202402.1.0/otBannerSdk.js105 KB56 KB (54%)✓3rd
https://stackoverflow.blog/_nuxt/DSwynrvu.js81 KB29 KB (36%)✓3rd
https://stackoverflow.blog/_nuxt/CsFSaSiq.js3 KB—✓3rd
https://stackoverflow.blog/_nuxt/fU7N0oAU.js3 KB—✓3rd
https://stackoverflow.blog/_nuxt/Be2TR9AJ.js3 KB—✓3rd
https://stackoverflow.blog/_nuxt/Domw9ns6.js5 KB—✓3rd
https://stackoverflow.blog/_nuxt/CngAv1rp.js5 KB—✓3rd
https://stackoverflow.blog/_nuxt/7xjXSHum.js22 KB—✓3rd
https://stackoverflow.blog/_nuxt/jfbhR9Vy.js9 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

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

Green Hosting

No green hosting detected

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
Image Optimization
27 images, 0 KB saveable
PASS
27 images, 0 KB saveable
Info::
All images are well-optimized
27 images 412 KB
0 oversized -0 KB
2 legacy format
0 missing dimensions CLS risk
A+
Font Loading
3 fonts (111 KB)
PASS
3 fonts (111 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

111 KB total

Render-blocking

0

of 3

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s FCP 880 ms LCP 1.3 shttps://stackoverflow.blog/_nuxt/StackSansText_wght_.OTiTLYhg.woff2StackSansText_wght_.OTi... https://stackoverflow.blog/_nuxt/StackSansText_wght_.OTiTLYhg.woff2 — 50.3 KiB — 0 ms — font-display: swaphttps://stackoverflow.blog/_nuxt/StackSansHeadline_wght_.drIOpmpO.woff2StackSansHeadline_wght_... https://stackoverflow.blog/_nuxt/StackSansHeadline_wght_.drIOpmpO.woff2 — 50.3 KiB — 0 ms — font-display: swaphttps://web-player.art19.com/assets/fonts/fontello-effa7ce16fec99765628d80aa7ccf970.woff?62349305fontello-effa7ce16fec99... https://web-player.art19.com/assets/fonts/fontello-effa7ce16fec99765628d80aa7ccf970.woff?62349305 — 10.3 KiB — 0 ms — font-display: swap
StackSansText_wght_.OTi... woff2 swap
Size 50 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
StackSansHeadline_wght_... woff2 swap
Size 50 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
fontello-effa7ce16fec99... woff swap
Size 10 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
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)

Fixing the unchecked items could save ~3 KB and ~6 ms

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
79 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
100% of JavaScript execution is third-party
First-party Third-party 558ms · 284KB · €6/mo
Unattributable
Other
Costly
Execution 261ms
Transfer 0 KB
Monthly Cost €3/mo
stackoverflow.blog
Other
Optional
Execution 171ms
Transfer 28 KB
Monthly Cost €2/mo
OneTrust
Consent
Essential
Execution 70ms
Transfer 105 KB
Unused 54%
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 56ms
Transfer 151 KB
Unused 42%
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • Unattributable adds 261ms and costs ~€3/month

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

Unattributable takes 261ms 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

54% of OneTrust'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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