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https://bsky.app

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
74
GRADE
C
FIX
5
REVIEW
1
PASS
6
INFO
2

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

Mobile Desktop
40
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
77
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.

620 ms

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

4.55 s

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

1.31 s

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.

3.72 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.

4.59 s

Page Load Progression

439 ms
878 ms
1.3 s
1.8 s
2.2 s
2.6 s
3.1 s
3.5 s
Checks
14
6 PASS 1 REVIEW 5 FIX
F
Page Weight Budget
Action
3.4 MB transferred, 82 requests
FIX
3.4 MB transferred, 82 requests
Warning::
Page weighs 9.0 MB (3.4 MB transferred)
Warning::
JavaScript is 2.2 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 2.2 MB
Info::
Fonts are 345 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 345 KB
Info::
82 HTTP requests
Info::
Estimated 0.71 g CO2 per page load
3.4 MB / 2.4 MB budget
3.4 MB transferred
82 requests
0.71 g CO2 per page load
JavaScript 2.2 MiB 66%
Images 789.0 KiB 23%
Fonts 345.1 KiB 10%
Other 52.6 KiB 2%
CSS 3.4 KiB 0%
Other 3.3 KiB 0%
HTML 3.2 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

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

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 (3.4 MiB of 3.4 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Execution Cost
Action
2948ms total JS execution
FIX
2948ms total JS execution
Warning::
https://web-cdn.bsky.app/static/js/8918.42b29087.j...: 1825ms CPU time
Warning::
https://web-cdn.bsky.app/static/js/main.53d50458.j...: 744ms CPU time
Info::
Unattributable: 231ms CPU time
Info::
https://bsky.app/: 147ms CPU time
Warning::
Third-party scripts: 2801ms (95% of total)

Main Thread Breakdown

Script Evaluation 72% Other 10% Script Parsing & Compilation 8% Style & Layout 6%
ScriptTotalScriptingParse/CompileParty
https://web-cdn.bsky.app/static/js/8918.42b29087.js1825ms1399ms133ms3rd
https://web-cdn.bsky.app/static/js/main.53d50458.js744ms639ms83ms3rd
Unattributable231ms90ms0ms3rd
https://bsky.app/147ms4ms0ms1st
F
JS Bundles
Action
4 scripts, 1.4 MB unused
FIX
4 scripts, 1.4 MB unused
Warning::
https://web-cdn.bsky.app/static/js/main.53d50458.j...: 656 KB unused (76%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://web-cdn.bsky.app/static/js/8918.42b29087.j...: 586 KB unused (49%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://web-cdn.bsky.app/static/js/8930.c7cd4580.c...: 150 KB unused (91%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 1.4 MB
1392 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://web-cdn.bsky.app/static/js/main.53d50458.js865 KB656 KB (76%)✓3rd
https://web-cdn.bsky.app/static/js/8918.42b29087.js1201 KB586 KB (49%)✓3rd
https://web-cdn.bsky.app/static/js/8930.c7cd4580.chunk.js166 KB150 KB (91%)✓3rd
https://web-cdn.bsky.app/static/js/7090.61b26aef.chunk.js53 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

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.

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
54 images, 0 KB saveable
PASS
54 images, 0 KB saveable
Info::
All images are well-optimized
54 images 789 KB
0 oversized -0 KB
3 legacy format
0 missing dimensions CLS risk
A+
Font Loading
1 fonts (345 KB)
PASS
1 fonts (345 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

345 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 1.0 s 2.0 s 3.0 s 4.0 s FCP 620 ms LCP 4.6 shttps://web-cdn.bsky.app/static/media/InterVariable.c504db5c06caaf7cdfba.woff2InterVariable.c504db5c0... https://web-cdn.bsky.app/static/media/InterVariable.c504db5c06caaf7cdfba.woff2 — 345.1 KiB — 0 ms — font-display: swap
InterVariable.c504db5c0... woff2 swap
Size 345 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
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 ~173 KB and ~346 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
82 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
95% of JavaScript execution is third-party
First-party Third-party 2801ms · 2066KB · $37/mo
web-cdn.bsky.app
Other
Costly
Execution 1825ms
Transfer 1201 KB
Unused 49%
Monthly Cost $24/mo
web-cdn.bsky.app
Other
Costly
Execution 744ms
Transfer 865 KB
Unused 76%
Monthly Cost $10/mo
Unattributable
Other
Costly
Execution 231ms
Transfer 0 KB
Monthly Cost $3/mo

These scripts may cost more than they're worth

  • web-cdn.bsky.app adds 1825ms and costs ~$24/month
  • web-cdn.bsky.app adds 744ms and costs ~$10/month
  • Unattributable adds 231ms and costs ~$3/month

95% 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

web-cdn.bsky.app takes 1825ms 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

web-cdn.bsky.app takes 744ms 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

76% of web-cdn.bsky.app'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

Unattributable takes 231ms 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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