Performance

· 22 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

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.

854 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.

0.000

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

1.40 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

375 ms

750 ms

1.1 s

1.5 s

1.9 s

2.2 s

2.6 s

3.0 s

Checks

9 PASS 6 REVIEW 4 FIX

Page Weight Budget

Action

6.4 MB transferred, 39 requests

FIX

6.4 MB transferred, 39 requests

Page weighs 7.2 MB (6.4 MB transferred)

Images are 6.0 MB — compress or use modern formats

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Got: 6.0 MB

39 HTTP requests

Estimated 1.3 g CO2 per page load

6.4 MB transferred

39 requests

1.3 g CO2 per page load

Images 6.0 MiB 94%

Fonts 154.4 KiB 2%

JavaScript 119.6 KiB 2%

CSS 113.8 KiB 2%

HTML 9.0 KiB 0%

Other 251 B 0%

0 2.4 MB 4.9 MB

Over budget

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Why this matters

Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.

Source: web.dev

Third-Party Impact

Action

100% third-party, 0 ms blocking

FIX

100% third-party, 0 ms blocking

Third-party code accounts for 100% of page weight (6.4 MiB of 6.4 MiB)

Third-party blocking time is low (0 ms)

100%

First-party Third-party

Page Weight Inventory

Action

39 resources · 6.4 MB · 0 KB savings available

FIX

39 resources · 6.4 MB · 0 KB savings available

Page weight 6.4 MB exceeds 1 MB target by 5.4 MB

Got: 6.4 MB Expected: ≤ 1 MB

38 third-party resources (100% of weight)

6 resources over 200KB

39 resources · 6.4 MiB · 38 third-party 5.4 MiB over 1MB target

Image 94% · 6.0 MiB

Font 2% · 154.4 KiB

JavaScript 2% · 119.6 KiB

CSS 2% · 113.8 KiB

Document 0% · 9.2 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

39 resources			6.4 MiB

HTTP Caching

Action

No cache headers

FIX

No cache headers

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.

Image Optimization

13 images, 0 KB saveable

REVIEW

13 images, 0 KB saveable

https://www.autoskolanemec.cz/images/assets/logo.p... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

13 images 6.0 MB

0 oversized -0 KB

12 legacy format

1 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

HTTP/3 (QUIC)

HTTP/3 not advertised

REVIEW

HTTP/3 not advertised

HTTP/3 (QUIC) is not advertised

HTTP/3 isn't advertised via Alt-Svc and the worker didn't negotiate h3. HTTP/3 reduces handshake latency (1-RTT instead of 2-3 RTTs) and is more resilient on lossy connections. Most modern CDNs (Cloudflare, Fastly, AWS CloudFront, Google Cloud CDN) support HTTP/3 with a single config switch -- consider enabling for mobile-heavy workloads.

Compression Algorithm

Action

Main response served uncompressed

REVIEW

Main response served uncompressed

Main HTML response has no Content-Encoding (uncompressed)

The main HTML document is served without compression. The Text Compression section above lists the broader picture; for the main response specifically, even gzip would shave ~70-80% off most text payloads.

Main HTML Cache-Control

No Cache-Control header on main HTML response

REVIEW

No Cache-Control header on main HTML response

Main HTML response has no Cache-Control header

Without an explicit Cache-Control, browsers fall back to heuristic caching (~10% of Last-Modified age). Set `Cache-Control: no-cache` or `max-age=300` for HTML to control freshness explicitly -- prevents stale auth state and SPA shell drift.

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.

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

All text resources are properly compressed.

A+

JS Execution Cost

295ms total JS execution

PASS

295ms total JS execution

https://www.autoskolanemec.cz/: 140ms CPU time

Unattributable: 102ms CPU time

https://www.autoskolanemec.cz/templates/g5_helium/...: 53ms CPU time

Third-party scripts: 193ms (66% of total)

Main Thread Breakdown

Other 38% Style & Layout 30% Script Evaluation 18% Parse HTML & CSS 6% Rendering 4%

Script	Total	Scripting	Parse/Compile	Party
https://www.autoskolanemec.cz/	140ms	1ms	1ms	3rd
Unattributable	102ms	2ms	0ms	1st
https://www.autoskolanemec.cz/templates/g5_helium/custom/js/jluikit.min.js	53ms	22ms	2ms	3rd

A+

Font Loading

2 fonts (154 KB)

PASS

2 fonts (154 KB)

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

Web fonts

154 KB total

Render-blocking

of 2

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

fa-solid-900.woff2 woff2 swap

Size 79 KB

Load time 48 ms

Start 1.4 s

Risk FOUT — text flashes from fallback to web font

fa-brands-400.woff2 woff2 swap

Size 76 KB

Load time 82 ms

Start 1.4 s

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

8 scripts, 0 KB unused

PASS

8 scripts, 0 KB unused

0 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://www.autoskolanemec.cz/media/system/js/core.min.js?17121a112ecec3d656efe5c5f493429c9acf2179	3 KB	—	✓	3rd
https://www.autoskolanemec.cz/media/system/js/messages.min.js?7425e8d1cb9e4f061d5e30271d6d99b085344117	2 KB	—	✓	3rd
https://www.autoskolanemec.cz/media/vendor/jquery/js/jquery.min.js?3.6.0	31 KB	—	✓	3rd
https://www.autoskolanemec.cz/templates/g5_helium/custom/js/jluikit.min.js	28 KB	—	✓	3rd
https://www.autoskolanemec.cz/media/gantry5/assets/js/main.js	17 KB	—	✓	3rd
https://www.autoskolanemec.cz/plugins/system/gdpr/assets/js/jquery.fancybox.min.js?e5d29c0557269a8c5fbd07ac159388b4	19 KB	—	✓	3rd
https://www.autoskolanemec.cz/plugins/system/gdpr/assets/js/cookieconsent.min.js?e5d29c0557269a8c5fbd07ac159388b4	13 KB	—	✓	3rd
https://www.autoskolanemec.cz/plugins/system/gdpr/assets/js/init.js?e5d29c0557269a8c5fbd07ac159388b4	6 KB	—	✓	3rd

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

No optimization needed

PASS

No optimization needed

No resource hint issues

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+

Server Response Intelligence

1 server-response signal(s) detected

PASS

1 server-response signal(s) detected

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.

Network Waterfall

39 requests over 1686ms

INFO

HTML JavaScript CSS Images Fonts XHR/Fetch Other

Third-Party Script Cost

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

INFO

66% of JavaScript execution is third-party

First-party Third-party 193ms · 37KB · Kč24/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
www.autoskolanemec.cz www.autoskolanemec.cz	Other	140ms	9 KB	—	Kč17/mo	Optional
www.autoskolanemec.cz www.autoskolanemec.cz	Other	53ms	28 KB	—	Kč7/mo	Optional

www.autoskolanemec.cz

Other

Optional

Execution 140ms

Transfer 9 KB

Monthly Cost Kč17/mo

www.autoskolanemec.cz

Other

Optional

Execution 53ms

Transfer 28 KB

Monthly Cost Kč7/mo

66% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

Learn more ▾

Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

How third-party costs are calculated

Image Optimization

11 images, 3998 KB total, 3278 KB wasted

INFO

Image Optimization Audit

Total Images

Total Size

3998 KB

Oversized

Wasted

3278 KB

1 missing dimensions 8 missing lazy loading

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