Skip to content
https://golang.org

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
82
GRADE
B
FIX
3
REVIEW
2
PASS
7
INFO
2

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

Mobile Desktop
54
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
88
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
92
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
85
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.

3.86 s

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

7.20 s

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

515 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.

3.92 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.

7.24 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
7 PASS 2 REVIEW 3 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 (827.0 KiB of 828.0 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Execution Cost
Action
2702ms total JS execution
FIX
2702ms total JS execution
Warning::
Unattributable: 1113ms CPU time
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-W8M...: 624ms CPU time
Warning::
https://go.dev/: 448ms CPU time
Warning::
https://www.googletagmanager.com/gtag/js?id=G-HL38...: 294ms CPU time
Info::
https://go.dev/js/index.js: 96ms CPU time
Warning::
Third-party scripts: 2702ms (100% of total)

Main Thread Breakdown

Other 40% Script Evaluation 31% Style & Layout 13% Script Parsing & Compilation 10%
ScriptTotalScriptingParse/CompileParty
Unattributable1113ms17ms0ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-W8MVQXG624ms398ms220ms3rd
https://go.dev/448ms32ms3ms3rd
https://www.googletagmanager.com/gtag/js?id=G-HL38R6X1Q3&cx=c&gtm=4e6411294ms226ms44ms3rd
https://go.dev/js/index.js96ms53ms1ms3rd
https://go.dev/js/jquery.js64ms51ms9ms3rd
https://www.google-analytics.com/analytics.js62ms50ms5ms3rd
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
Image Optimization
Action
47 images, 0 KB saveable
REVIEW
47 images, 0 KB saveable
Warning::
https://go.dev/images/logos/social/github.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/logos/social/reddit.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/logos/social/stack-overflow.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/logos/social/mastodon.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/gophers/pilot-bust.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/google-white.png is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/logos/social/slack.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/icons/package.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/logos/social/bluesky.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/icons/command-folder.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/icons/code.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/icons/gear.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/logos/social/google-groups.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/logos/social/twitter.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://go.dev/images/icons/sphere.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
47 images 241 KB
0 oversized -0 KB
46 legacy format
15 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

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 Bundles
13 scripts, 130 KB unused
REVIEW
13 scripts, 130 KB unused
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-W8M...: 68 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-HL38...: 62 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 130 KB
130 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtm.js?id=GTM-W8MVQXG157 KB68 KB (43%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-HL38R6X1Q3&cx=c&gtm=4e6411142 KB62 KB (43%)✓3rd
https://go.dev/js/hats.js1 KB—✓3rd
https://go.dev/js/carousels.js2 KB—✓3rd
https://go.dev/js/searchBox.js1 KB—✓3rd
https://go.dev/js/misc.js2 KB—✓3rd
https://go.dev/js/site.js4 KB—✓3rd
https://go.dev/js/playground.js6 KB—✗3rd
https://go.dev/js/godocs.js4 KB—✓3rd
https://go.dev/js/copypaste.js0 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

A
Page Weight Budget
828 KB transferred, 73 requests
PASS
828 KB transferred, 73 requests
Info::
Page weighs 1.6 MB (828 KB transferred)
Info::
73 HTTP requests
Info::
Estimated 0.17 g CO2 per page load
828 KB / 2.4 MB budget
828 KB transferred
73 requests
0.17 g CO2 per page load
JavaScript 376.6 KiB 45%
Images 240.7 KiB 29%
Fonts 125.6 KiB 15%
Other 32.2 KiB 4%
CSS 27.2 KiB 3%
HTML 12.7 KiB 2%
Other 12.2 KiB 1%
Other 778 B 0%
0 2.4 MB 4.9 MB
Under budget
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 (126 KB)
PASS
1 fonts (126 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

126 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 5.0 s 6.0 s 7.0 s FCP 3.9 s LCP 7.2 shttps://fonts.gstatic.com/s/materialicons/v145/flUhRq6tzZclQEJ-Vdg-IuiaDsNcIhQ8tQ.woff2flUhRq6tzZclQEJ-Vdg-Iui... https://fonts.gstatic.com/s/materialicons/v145/flUhRq6tzZclQEJ-Vdg-IuiaDsNcIhQ8tQ.woff2 — 125.6 KiB — 0 ms — font-display: swap
flUhRq6tzZclQEJ-Vdg-Iui... woff2 swap
Size 126 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 ~63 KB and ~126 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
1 hints, 0 missing preconnects
PASS
1 hints, 0 missing preconnects
Info::
Page uses 1 resource hint(s)

Current Resource Hints

preconnect
1
preload
—
dns-prefetch
—
prefetch
—

1 resource hints configured

A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Google Cloud

Network Waterfall
73 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 2702ms · 369KB · €29/mo
Unattributable
Other
Costly
Execution 1113ms
Transfer 0 KB
Monthly Cost €12/mo
Google Tag Manager
Tag Manager
Costly
Execution 624ms
Transfer 157 KB
Unused 43%
Monthly Cost €7/mo
go.dev
Other
Costly
Execution 448ms
Transfer 13 KB
Monthly Cost €5/mo
Google Tag Manager
Tag Manager
Costly
Execution 294ms
Transfer 142 KB
Unused 43%
Monthly Cost €3/mo
go.dev
Other
Optional
Execution 96ms
Transfer 1 KB
Monthly Cost €1/mo
go.dev
Other
Optional
Execution 64ms
Transfer 36 KB
Monthly Cost €1/mo
Google Analytics
Analytics
Optional
Execution 62ms
Transfer 21 KB
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • Unattributable adds 1113ms and costs ~€12/month
  • Google Tag Manager adds 624ms and costs ~€7/month
  • go.dev adds 448ms and costs ~€5/month
  • Google Tag Manager adds 294ms 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 1113ms 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

Google Tag Manager takes 624ms 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

go.dev takes 448ms 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

Google Tag Manager takes 294ms 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.

Send Feedback