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https://bsky.app

Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
74
GRADE
C
FIX
5
REVIEW
1
PASS
8
INFO
2

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

Mobile Desktop
32
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
74
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.

2.55 s

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

20.36 s

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

4.31 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.

13.25 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.

22.74 s

Page Load Progression

572 ms
1.1 s
1.7 s
2.3 s
2.9 s
3.4 s
4.0 s
4.6 s
Checks
16
8 PASS 1 REVIEW 5 FIX
F
Page Weight Budget
Action
3.5 MB transferred, 68 requests
FIX
3.5 MB transferred, 68 requests
Warning::
Page weighs 9.0 MB (3.5 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::
68 HTTP requests
Info::
Estimated 0.73 g CO2 per page load
3.5 MB / 2.4 MB budget
3.5 MB transferred
68 requests
0.73 g CO2 per page load
JavaScript 2.2 MiB 65%
Images 864.0 KiB 24%
Fonts 345.0 KiB 10%
Other 37.2 KiB 1%
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 (3.5 MiB of 3.5 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
JS Execution Cost
Action
9873ms total JS execution
FIX
9873ms total JS execution
Warning::
https://web-cdn.bsky.app/static/js/8918.42b29087.j...: 5453ms CPU time
Warning::
https://web-cdn.bsky.app/static/js/main.53d50458.j...: 2954ms CPU time
Warning::
Unattributable: 871ms CPU time
Warning::
https://bsky.app/: 416ms CPU time
Info::
https://web-cdn.bsky.app/static/js/8930.c7cd4580.c...: 180ms CPU time
Warning::
Third-party scripts: 9457ms (96% of total)

Main Thread Breakdown

Script Evaluation 68% Other 12% Script Parsing & Compilation 11% Style & Layout 5%
ScriptTotalScriptingParse/CompileParty
https://web-cdn.bsky.app/static/js/8918.42b29087.js5453ms3867ms598ms3rd
https://web-cdn.bsky.app/static/js/main.53d50458.js2954ms2480ms421ms3rd
Unattributable871ms247ms0ms3rd
https://bsky.app/416ms11ms1ms1st
https://web-cdn.bsky.app/static/js/8930.c7cd4580.chunk.js180ms109ms69ms3rd
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...: 663 KB unused (77%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://web-cdn.bsky.app/static/js/8918.42b29087.j...: 590 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
1403 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://web-cdn.bsky.app/static/js/main.53d50458.js867 KB663 KB (77%)✓3rd
https://web-cdn.bsky.app/static/js/8918.42b29087.js1199 KB590 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
42 images, 0 KB saveable
PASS
42 images, 0 KB saveable
Info::
All images are well-optimized
42 images 864 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 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s 14.0 s 16.0 s 18.0 s 20.0 s FCP 2.5 s LCP 20.4 shttps://web-cdn.bsky.app/static/media/InterVariable.c504db5c06caaf7cdfba.woff2InterVariable.c504db5c0... https://web-cdn.bsky.app/static/media/InterVariable.c504db5c06caaf7cdfba.woff2 — 345.0 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
3 hints, 0 missing preconnects
PASS
3 hints, 0 missing preconnects
Info::
Page uses 3 resource hint(s)

Current Resource Hints

preconnect
2
preload
1
dns-prefetch
—
prefetch
—

3 resource hints configured

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
68 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
96% of JavaScript execution is third-party
First-party Third-party 9457ms · 2231KB · $126/mo
web-cdn.bsky.app
Other
Costly
Execution 5453ms
Transfer 1199 KB
Unused 49%
Monthly Cost $72/mo
web-cdn.bsky.app
Other
Costly
Execution 2954ms
Transfer 867 KB
Unused 77%
Monthly Cost $39/mo
Unattributable
Other
Costly
Execution 871ms
Transfer 0 KB
Monthly Cost $12/mo
web-cdn.bsky.app
Other
Optional
Execution 180ms
Transfer 166 KB
Unused 91%
Monthly Cost $2/mo

These scripts may cost more than they're worth

  • web-cdn.bsky.app adds 5453ms and costs ~$72/month
  • web-cdn.bsky.app adds 2954ms and costs ~$39/month
  • Unattributable adds 871ms and costs ~$12/month

96% 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 5453ms 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 2954ms 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

77% 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 871ms 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

91% 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

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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