https://koloseum.com.pl
Performance
· 26 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.SCORE
88
GRADE
B
FIX
1
REVIEW
7
PASS
15
INFO
3
Performance-focused optimization plan with CWV assessment, top offenders, and time estimates
64
77
100
92
First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.
3.99 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
12.32 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
45 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.009
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
4.73 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.
12.34 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 sChecks
2615 PASS 7 REVIEW 1 FIX
DHTTP CachingActionno-store (uncacheable)FIX
HTTP Caching
Actionno-store (uncacheable)
no-store (uncacheable)
Info::
Cache-Control: no-store prevents all caching
Intentional for dynamic content, but increases server load for every page view.
Got: no-store, no-cache, must-revalidate
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control
no-store, no-cache, must-revalidate
| Directive | Value | Meaning |
|---|---|---|
| no-store | — | Never cache this response |
| no-cache | — | Cache but always revalidate first |
| must-revalidate | — | Must recheck with server after expiry |
CPage Weight BudgetAction1.9 MB transferred, 52 requestsREVIEW
Page Weight Budget
Action1.9 MB transferred, 52 requests
1.9 MB transferred, 52 requests
Info::
Page weighs 3.7 MB (1.9 MB transferred)
Warning::
Images are 1.3 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 1.3 MB
Warning::
JavaScript is 512 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 512 KB
Info::
52 HTTP requests
Info::
Estimated 0.41 g CO2 per page load
1.9 MB transferred
52 requests
0.41 g CO2 per page load
Images 1.3 MiB 65%
JavaScript 511.8 KiB 26%
Fonts 125.5 KiB 6%
CSS 42.4 KiB 2%
HTML 5.5 KiB 0%
Other 4.7 KiB 0%
Other 46 B 0%
0 2.4 MB 4.9 MB
Approaching limit
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
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
CImage OptimizationAction9 images, 0 KB saveableREVIEW
Image Optimization
Action9 images, 0 KB saveable
9 images, 0 KB saveable
Warning::
https://koloseum.com.pl/assets/images/app/banners/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://koloseum.com.pl/assets/images/app/logo.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://koloseum.com.pl/assets/images/app/banners/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://koloseum.com.pl/assets/images/app/banners/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
9 images 1.3 MB
0 oversized -0 KB
7 legacy format
4 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
CJS Execution CostAction1903ms total JS executionREVIEW
JS Execution Cost
Action1903ms total JS execution
1903ms total JS execution
Warning::
https://koloseum.com.pl/: 1042ms CPU time
Warning::
Unattributable: 524ms CPU time
Warning::
https://koloseum.com.pl/assets/js/jquery-3.3.1.min...: 337ms CPU time
Main Thread Breakdown
Other 45% Style & Layout 31% Script Evaluation 14% Rendering 4% Parse HTML & CSS 4%
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://koloseum.com.pl/ | 1042ms | 6ms | 2ms | 1st |
| Unattributable | 524ms | 6ms | 0ms | 1st |
| https://koloseum.com.pl/assets/js/jquery-3.3.1.min.js | 337ms | 220ms | 14ms | 1st |
BServer-Timing ObservabilityNo Server-Timing header foundREVIEW
Server-Timing Observability
No Server-Timing header found
No Server-Timing header found
Info::
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.
CPage Weight InventoryAction52 resources · 1.9 MB · 0 KB savings availableREVIEW
Page Weight Inventory
Action52 resources · 1.9 MB · 0 KB savings available
52 resources · 1.9 MB · 0 KB savings available
Warning::
Page weight 1.9 MB exceeds 1 MB target by 964 KB
Got: 1.9 MB Expected: ≤ 1 MB
Info::
27 third-party resources (27% of weight)
Info::
2 resources over 200KB
52 resources · 1.9 MiB · 27 third-party 963.6 KiB over 1MB target
Image 66% · 1.3 MiB
JavaScript 26% · 511.8 KiB
Font 6% · 125.5 KiB
CSS 2% · 42.4 KiB
Document 0% · 5.5 KiB
Other 0% · 46 B
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 52 resources | 1.9 MiB | ||||||
BJavaScript Blocking1 JS blocking issue(s) detectedREVIEW
JavaScript Blocking
1 JS blocking issue(s) detected
1 JS blocking issue(s) detected
Warning::
7 render-blocking <script src> tag(s) without async/defer
Each `<script src=...>` without `async`, `defer`, or `type="module"` blocks HTML parsing while the browser fetches and executes it. The block lasts the entire round-trip + execution time -- on slow networks this translates directly into LCP delay. Add `defer` (executes after parse, in source order) for scripts that interact with the DOM, or `async` (executes whenever ready) for analytics / independent scripts. Module scripts (`type="module"`) are deferred by default.
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
ActionWhether the site is served from green-energy infrastructure
Green Hosting
No green hosting detected
AThird-Party Impact27% third-party, 0 ms blockingPASS
Third-Party Impact
27% third-party, 0 ms blocking
27% third-party, 0 ms blocking
Info::
Third-party code accounts for 27% of page weight (528.1 KiB of 1.9 MiB)
Info::
Third-party blocking time is low (0 ms)
73%
27%
First-party Third-party
A+Text CompressionAll text resources are compressedPASS
Text Compression
All text resources are compressed
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+Font Loading7 fonts (126 KB)PASS
Font Loading
7 fonts (126 KB)
7 fonts (126 KB)
Info::
7 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
7
126 KB total
Render-blocking
0
of 7
Dominant font-display
swap
Most common across fonts
Font loading timeline
Transfer FOIT (block) FOUT (swap)
S6u9w4BMUTPHh6UVSwiPGQ3... woff2 swap
Size 14 KB
Load time 11 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6uyw4BMUTPHjx4wXiWtFCc... woff2 swap
Size 14 KB
Load time 14 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
fontawesome-webfont.woff2 woff2 swap
Size 76 KB
Load time 509 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh7USSwiPGQ3... woff2 swap
Size 14 KB
Load time 14 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh6UVSwaPGQ3... woff2 swap
Size 3 KB
Load time 36 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6uyw4BMUTPHjxAwXiWtFCf... woff2 swap
Size 3 KB
Load time 32 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh7USSwaPGQ3... woff2 swap
Size 3 KB
Load time 16 ms
Start 1.0 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 Bundles20 scripts, 0 KB unusedPASS
JS Bundles
20 scripts, 0 KB unused
20 scripts, 0 KB unused
0 KB unused JavaScript
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://koloseum.com.pl/assets/js/jquery-3.3.1.min.js | 29 KB | — | ✓ | 1st |
| https://koloseum.com.pl/assets/js/tether.min.js | 7 KB | — | ✓ | 1st |
| https://koloseum.com.pl/assets/js/bootstrap.min.js | 13 KB | — | ✓ | 1st |
| https://koloseum.com.pl/assets/js/fancybox/jquery.fancybox.min.js | 19 KB | — | ✓ | 1st |
| https://koloseum.com.pl/assets/js/wow/wow.min.js | 3 KB | — | ✓ | 1st |
| https://koloseum.com.pl/assets/js/owl-carousel/owl.carousel.min.js | 11 KB | — | ✓ | 1st |
| https://koloseum.com.pl/assets/js/site.js | 1 KB | — | ✓ | 1st |
| https://maps.gstatic.com/maps-api-v3/embed/js/66/2d/init_embed.js | 75 KB | — | ✓ | 3rd |
| https://maps.googleapis.com/maps/api/js?key=AIzaSyCmL18misQw9KdwqGaw3zHkitj8vG6QF2Y&paint_origin=&libraries=geometry,search&v=weekly&loading=async&language=en_US&experimentation=allowed&callback=onApiLoad | 3 KB | — | ✓ | 3rd |
| https://maps.googleapis.com/maps-api-v3/api/js/66/2d/search.js | 1 KB | — | ✓ | 3rd |
A+Resource CachingAll resources properly cachedPASS
Resource Caching
All resources properly cached
All resources properly cached
Info::
No caching issues found
All static resources have appropriate caching headers.
A+Critical Rendering PathNo render-blocking resourcesPASS
Critical Rendering Path
No render-blocking resources
No render-blocking resources
Info::
No render-blocking resources detected
A+Resource HintsNo optimization neededPASS
Resource Hints
No optimization needed
No optimization needed
Info::
No resource hint issues
A+HTTP/3 (QUIC)HTTP/3 advertised via Alt-SvcPASS
HTTP/3 (QUIC)
HTTP/3 advertised via Alt-Svc
HTTP/3 advertised via Alt-Svc
Info::
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+Compression AlgorithmMain response uses brotliPASS
Compression Algorithm
Main response uses brotli
Main response uses brotli
Info::
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 PreloadLCP preload audit not availablePASS
LCP Image Preload
LCP preload audit not available
LCP preload audit not available
Info::
LCP image preload audit not available for this scan
A+Main HTML Cache-ControlMain HTML uses no-store -- correct for sensitive/dynamic contentPASS
Main HTML Cache-Control
Main HTML uses no-store -- correct for sensitive/dynamic content
Main HTML uses no-store -- correct for sensitive/dynamic content
Info::
Main HTML uses no-store -- correct for sensitive/dynamic content
Got: no-store, no-cache, must-revalidate
A+Server Response Intelligence2 server-response signal(s) detectedPASS
Server Response Intelligence
2 server-response signal(s) detected
2 server-response signal(s) detected
Info::
`Vary` header declared: Accept-Encoding,User-Agent
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).
Info::
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.
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
Render-Blocking Resources
No render-blocking resources detected
No render-blocking resources detected
Info::
No render-blocking resources detected in <head>
A+Third-Party ResourcesNo third-party resources detectedPASS
Third-Party Resources
No third-party resources detected
No third-party resources detected
ACSS Performance Depth1 CSS depth issue(s) detectedPASS
CSS Performance Depth
1 CSS depth issue(s) detected
1 CSS depth issue(s) detected
Warning::
10 render-blocking stylesheet(s) -- recommended: <=3
Each `<link rel="stylesheet">` without a non-blocking `media` attribute holds up the first paint. Browsers download all of them before painting any content. Consolidate into 1-2 critical-path stylesheets; defer non-critical CSS via `<link rel="stylesheet" media="print" onload="this.media='all'">` or via the loadCSS pattern; inline above-the-fold CSS in `<style>` to short-circuit the request entirely.
Network Waterfall52 requests over 2567msINFO
Network Waterfall
52 requests over 2567ms
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Real-User Performance (CrUX)Field metrics from the Chrome User Experience ReportINFO
Real-User Performance (CrUX)
Field metrics from the Chrome User Experience Report
Chrome User Experience (CrUX)
Real-user metrics from the Chrome UX Report (2026-08-02 — 2026-08-29)
LCP (p75)
1641 ms
83% good
INP (p75)
84 ms
97% good
CLS (p75)
0.180
74% good
FCP (p75)
1154 ms
TTFB (p75)
775 ms
Image Optimization4 images, 268 KB total, 70 KB wastedINFO
Image Optimization
4 images, 268 KB total, 70 KB wasted
Image Optimization Audit
Total Images
4
Total Size
268 KB
Oversized
1
Wasted
70 KB
4 missing dimensions 3 missing lazy loading
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.