Performance

· 27 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.

SCORE

GRADE

FIX

REVIEW

PASS

INFO

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

Mobile Desktop

Performance

Accessibility

100

Best Practices

SEO

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

2.61 s

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

3.67 s

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

20 ms

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

0.003

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

2.61 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.

4.26 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

18 PASS 5 REVIEW

Third-Party Impact

45% third-party, 0 ms blocking

REVIEW

45% third-party, 0 ms blocking

Third-party code accounts for 45% of page weight (359.9 KiB of 802.1 KiB)

Third-party blocking time is low (0 ms)

55%

45%

First-party Third-party

JS Execution Cost

971ms total JS execution

REVIEW

971ms total JS execution

Unattributable: 344ms CPU time

https://esl-go.com/: 305ms CPU time

https://esl-go.com/assets/index-DfSHavb5.js: 241ms CPU time

https://apis.google.com/_/scs/abc-static/_/js/k=ga...: 81ms CPU time

Third-party scripts: 81ms (8% of total)

Main Thread Breakdown

Other 42% Script Evaluation 29% Style & Layout 21% Rendering 5%

Script	Total	Scripting	Parse/Compile	Party
Unattributable	344ms	6ms	0ms	1st
https://esl-go.com/	305ms	4ms	1ms	1st
https://esl-go.com/assets/index-DfSHavb5.js	241ms	199ms	3ms	1st
https://apis.google.com/_/scs/abc-static/_/js/k=gapi.lb.en.zhTT8Br0Ho8.O/m=gapi_iframes/rt=j/sv=1/d=1/ed=1/rs=AHpOoo-7LeULGjNQZRvhdu3G71akb6JY6A/cb=gapi.loaded_0?le=scs	81ms	70ms	7ms	3rd

JS Bundles

4 scripts, 90 KB unused

REVIEW

4 scripts, 90 KB unused

https://esl-go.com/assets/index-DfSHavb5.js: 90 KB unused (54%)

Consider code splitting or tree shaking to reduce unused code.

https://esl-go.com/assets/index-DfSHavb5.js: unminified — 29 KB could be saved

Total unused JavaScript: 90 KB

90 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://esl-go.com/assets/index-DfSHavb5.js	166 KB	90 KB (54%)	✗	1st
https://apis.google.com/js/api.js?onload=__iframefcb899536	6 KB	—	✓	3rd
https://apis.google.com/_/scs/abc-static/_/js/k=gapi.lb.en.zhTT8Br0Ho8.O/m=gapi_iframes/rt=j/sv=1/d=1/ed=1/rs=AHpOoo-7LeULGjNQZRvhdu3G71akb6JY6A/cb=gapi.loaded_0?le=scs	34 KB	—	✓	3rd
https://elevatelisteninglessons.firebaseapp.com/__/auth/iframe.js	93 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

Server-Timing Observability

No Server-Timing header found

REVIEW

No Server-Timing header found

Server-Timing exposes backend timing breakdowns to browser DevTools (e.g., `db: 45ms; render: 120ms; cache: 2ms`). Useful for diagnosing slow pages without backend log access. Most modern frameworks (Next.js, Cloudflare Workers, Fastly) emit it automatically; absence on a managed platform usually means telemetry headers are stripped at the edge.

HTTP Caching

public, max-age=0, must-revalidate

REVIEW

public, max-age=0, must-revalidate

Cache-Control header is set

Got: public, max-age=0, must-revalidate

No ETag or Last-Modified header

Conditional requests (304 Not Modified) are not possible without validators.

Cache-Control

public, max-age=0, must-revalidate

Directive	Value	Meaning
public	—	Any cache may store this response
max-age	0	Cache for 0 seconds
must-revalidate	—	Must recheck with server after expiry

Page Weight Budget

802 KB transferred, 19 requests

PASS

802 KB transferred, 19 requests

Page weighs 1.9 MB (802 KB transferred)

19 HTTP requests

Estimated 0.16 g CO2 per page load

802 KB transferred

19 requests

0.16 g CO2 per page load

Images 462.2 KiB 58%

JavaScript 299.4 KiB 37%

Fonts 26.7 KiB 3%

CSS 10.3 KiB 1%

HTML 1.7 KiB 0%

Other 1.4 KiB 0%

Other 395 B 0%

Other 0 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

All text resources are properly compressed.

A+

Image Optimization

6 images, 0 KB saveable

PASS

6 images, 0 KB saveable

All images are well-optimized

6 images 462 KB

0 oversized -0 KB

1 legacy format

0 missing dimensions CLS risk

A+

Font Loading

1 fonts (27 KB)

PASS

1 fonts (27 KB)

1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

27 KB total

Render-blocking

of 1

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

LDIoaomQNQcsA88c7O9yZ4K... woff2 swap

Size 27 KB

Load time 25 ms

Start 341 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+

Resource Caching

All resources properly cached

PASS

All resources properly cached

No caching issues found

All static resources have appropriate caching headers.

A+

Critical Rendering Path

No render-blocking resources

PASS

No render-blocking resources

No render-blocking resources detected

A+

Resource Hints

2 hints, 0 missing preconnects

PASS

2 hints, 0 missing preconnects

Page uses 2 resource hint(s)

Current Resource Hints

preconnect

preload

—

dns-prefetch

—

prefetch

—

2 resource hints configured

A+

HTTP/3 (QUIC)

HTTP/3 advertised via Alt-Svc

PASS

HTTP/3 advertised via Alt-Svc

HTTP/3 (QUIC) is supported

First-load mobile users on cellular networks see meaningful latency improvements with HTTP/3. The QUIC transport collapses TLS + TCP handshakes into one and recovers faster from packet loss.

A+

Document Compression

Document response uses brotli

PASS

Document response uses brotli

Main HTML response uses brotli (Content-Encoding: br)

Brotli is the best text-compression algorithm for general use, ~20% smaller than gzip on average (40% on smaller files). Modern browsers all support it.

A+

LCP Image Preload

LCP preload audit not available

PASS

LCP preload audit not available

LCP image preload audit not available for this scan

A+

Main HTML Cache-Control

Main HTML max-age=0 (≤ 5min) is appropriate

PASS

Main HTML max-age=0 (≤ 5min) is appropriate

Got: public, max-age=0, must-revalidate

A+

Server Response Intelligence

2 server-response signal(s) detected

PASS

2 server-response signal(s) detected

`Vary` header declared: accept-encoding

The page declares a `Vary` header, telling downstream caches which request headers the response varies on. Critical for content-negotiated responses (compression, language, cookies, device class).

No `ETag` or `Last-Modified` -- conditional GET not supported

Without either header, browsers can't issue conditional GETs and refresh always re-downloads the full response body even when nothing changed. Add `ETag: "<hash>"` (or `Last-Modified: <date>`) on cacheable responses; the server returns 304 Not Modified when the client's cached copy is still valid, saving bandwidth.

Page Weight Inventory

19 resources · 802 KB · 90 KB savings available

PASS

19 resources · 802 KB · 90 KB savings available

Within 1MB page-weight target

Got: 802 KB

~90 KB of savings available

14 third-party resources (45% of weight)

1 resources over 200KB

19 resources · 802.1 KiB · 14 third-party Within 1MB page-weight target

Image 58% · 462.2 KiB

JavaScript 37% · 299.4 KiB

Font 3% · 26.7 KiB

CSS 1% · 10.3 KiB

Other 0% · 1.8 KiB

Document 0% · 1.7 KiB

~89.9 KiB of savings available

Remove unused JavaScript: 89.9 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

19 resources			802.1 KiB

A+

Render-Blocking Resources

No render-blocking resources detected

PASS

No render-blocking resources detected

No render-blocking resources detected in <head>

A+

Third-Party Resources

No third-party resources detected

PASS

No third-party resources detected

A+

JavaScript Blocking

No render-blocking JS or document.write usage detected

PASS

No render-blocking JS or document.write usage detected

No JavaScript blocking issues detected

A+

CSS Performance Depth

No CSS performance depth issues detected

PASS

No CSS performance depth issues detected

A+

Green Hosting

Whether the site is served from green-energy infrastructure

PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

Asset Compression

No text asset hosts to measure

INFO

No text asset hosts to measure

No third-party or subdomain host served enough text assets to measure

Asset compression is measured per host, from one HEAD request against a sampled resource. Pages that serve all their JS and CSS from the document's own origin are covered by the document compression check instead.

Network Waterfall

19 requests over 1699ms

INFO

HTML JavaScript CSS Images Fonts XHR/Fetch Other

Third-Party Script Cost

Per-script blocking time, transfer cost, and cache headers

INFO

8% of JavaScript execution is third-party

First-party Third-party 81ms · 34KB · $0/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
apis.google.com apis.google.com	Other	81ms	34 KB	—	$0/mo	Optional

apis.google.com

Other

Optional

Execution 81ms

Transfer 34 KB

Monthly Cost $0/mo

How third-party costs are calculated

Image Optimization

8 images, 742 KB total, 429 KB wasted

INFO

Image Optimization Audit

Total Images

Total Size

742 KB

Oversized

Wasted

429 KB

8 missing dimensions 5 missing lazy loading

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.