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https://www.sublimetext.com

Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
95
GRADE
A
FIX
1
REVIEW
3
PASS
10
INFO
2

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

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

902 ms

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

1.13 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.

0.007

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

1.94 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.

1.13 s

Page Load Progression

416 ms
831 ms
1.2 s
1.7 s
2.1 s
2.5 s
2.9 s
3.3 s
Checks
16
10 PASS 3 REVIEW 1 FIX
D
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.
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present

No Cache-Control header

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

C
Image Optimization
Action
17 images, 0 KB saveable
REVIEW
17 images, 0 KB saveable
Warning::
https://www.sublimetext.com/images/icon_gpu.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sublimetext.com/images/icon_arm64.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sublimetext.com/images/icon_auto_compl... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sublimetext.com/images/icon_dark_mode.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sublimetext.com/images/icon_ts.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sublimetext.com/images/icon_syntax.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sublimetext.com/images/icon_python.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sublimetext.com/images/icon_tab_multi.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
17 images 353 KB
0 oversized -0 KB
16 legacy format
8 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

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

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

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

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

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

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

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

B
JS Execution Cost
541ms total JS execution
REVIEW
541ms total JS execution
Warning::
https://www.sublimetext.com/: 327ms CPU time
Info::
Unattributable: 213ms CPU time
Info::
Third-party scripts: 213ms (39% of total)

Main Thread Breakdown

Other 51% Style & Layout 26% Script Evaluation 10% Rendering 9%
ScriptTotalScriptingParse/CompileParty
https://www.sublimetext.com/327ms42ms4ms1st
Unattributable213ms6ms0ms3rd
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Page Weight Budget
473 KB transferred, 24 requests
PASS
473 KB transferred, 24 requests
Info::
Page weighs 546 KB (473 KB transferred)
Info::
24 HTTP requests
Info::
Estimated 0.10 g CO2 per page load
473 KB / 2.4 MB budget
473 KB transferred
24 requests
0.10 g CO2 per page load
Images 353.0 KiB 75%
Fonts 70.0 KiB 15%
Other 26.6 KiB 6%
CSS 9.1 KiB 2%
HTML 8.9 KiB 2%
JavaScript 6.0 KiB 1%
0 2.4 MB 4.9 MB
Under budget
A+
Third-Party Impact
16% third-party, 0 ms blocking
PASS
16% third-party, 0 ms blocking
Info::
Third-party code accounts for 16% of page weight (76.0 KiB of 473.5 KiB)
Info::
Third-party blocking time is low (0 ms)
84%
16%
First-party Third-party
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
3 fonts (70 KB)
PASS
3 fonts (70 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

70 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 902 ms LCP 1.1 shttps://www.sublimetext.com/fonts/lato-v16-latin-regular.woff2lato-v16-latin-regular.... https://www.sublimetext.com/fonts/lato-v16-latin-regular.woff2 — 23.2 KiB — 0 ms — font-display: swaphttps://www.sublimetext.com/fonts/lato-v16-latin-700.woff2lato-v16-latin-700.woff2 https://www.sublimetext.com/fonts/lato-v16-latin-700.woff2 — 22.7 KiB — 0 ms — font-display: swaphttps://www.sublimetext.com/fonts/lato-v16-latin-italic.woff2lato-v16-latin-italic.w... https://www.sublimetext.com/fonts/lato-v16-latin-italic.woff2 — 24.1 KiB — 0 ms — font-display: swap
lato-v16-latin-regular.... woff2 swap
Size 23 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
lato-v16-latin-700.woff2 woff2 swap
Size 23 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
lato-v16-latin-italic.w... woff2 swap
Size 24 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+
JS Bundles
1 scripts, 0 KB unused
PASS
1 scripts, 0 KB unused
0 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.sublimetext.com/screencasts/linux_dark.js?v26 KB—✓1st
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
24 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
39% of JavaScript execution is third-party
First-party Third-party 213ms · 0KB · $3/mo
Unattributable
Other
Costly
Execution 213ms
Transfer 0 KB
Monthly Cost $3/mo

These scripts may cost more than they're worth

  • Unattributable adds 213ms and costs ~$3/month

Unattributable takes 213ms 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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