https://koloseum.com.pl
Performance
· 22 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.SCORE
88
GRADE
B
FIX
1
REVIEW
5
PASS
13
INFO
3
Performance-focused optimization plan with CWV assessment, top offenders, and time estimates
64
79
100
92
First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.
1.59 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
1.88 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.
0.461
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
1.79 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.
1.88 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
2213 PASS 5 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 1.2 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 1.2 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 0.40 g CO2 per page load
1.9 MB transferred
52 requests
0.40 g CO2 per page load
Images 1.2 MiB 64%
JavaScript 511.8 KiB 26%
Fonts 141.9 KiB 7%
CSS 42.5 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 OptimizationAction7 images, 0 KB saveableREVIEW
Image Optimization
Action7 images, 0 KB saveable
7 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/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.
7 images 1.2 MB
0 oversized -0 KB
6 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
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 936 KB
Got: 1.9 MB Expected: ≤ 1 MB
Info::
27 third-party resources (26% of weight)
Info::
2 resources over 200KB
52 resources · 1.9 MiB · 27 third-party 936.5 KiB over 1MB target
Image 64% · 1.2 MiB
JavaScript 26% · 511.8 KiB
Font 7% · 141.9 KiB
CSS 2% · 42.5 KiB
Document 0% · 5.5 KiB
Other 0% · 46 B
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 52 resources | 1.9 MiB | ||||||
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 Impact26% third-party, 0 ms blockingPASS
Third-Party Impact
26% third-party, 0 ms blocking
26% third-party, 0 ms blocking
Info::
Third-party code accounts for 26% of page weight (501.0 KiB of 1.9 MiB)
Info::
Third-party blocking time is low (0 ms)
74%
26%
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+JS Execution Cost414ms total JS executionPASS
JS Execution Cost
414ms total JS execution
414ms total JS execution
Info::
https://koloseum.com.pl/: 247ms CPU time
Info::
Unattributable: 89ms CPU time
Info::
https://koloseum.com.pl/assets/js/jquery-3.3.1.min...: 78ms CPU time
Main Thread Breakdown
Other 44% Style & Layout 30% Script Evaluation 14% Rendering 6% Parse HTML & CSS 4%
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://koloseum.com.pl/ | 247ms | 2ms | 1ms | 1st |
| Unattributable | 89ms | 2ms | 0ms | 1st |
| https://koloseum.com.pl/assets/js/jquery-3.3.1.min.js | 78ms | 49ms | 2ms | 1st |
A+Font Loading9 fonts (142 KB)PASS
Font Loading
9 fonts (142 KB)
9 fonts (142 KB)
Info::
9 font(s) use font-display: swap (FOUT risk but functional)
Web fonts
9
142 KB total
Render-blocking
0
of 9
Dominant font-display
swap
Most common across fonts
Font loading timeline
Transfer FOIT (block) FOUT (swap)
S6uyw4BMUTPHjx4wXiWtFCc... woff2 swap
Size 14 KB
Load time 13 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh50XSwiPGQ3... woff2 swap
Size 13 KB
Load time 18 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
fontawesome-webfont.woff2 woff2 swap
Size 75 KB
Load time 369 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh6UVSwiPGQ3... woff2 swap
Size 14 KB
Load time 23 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh7USSwiPGQ3... woff2 swap
Size 14 KB
Load time 29 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6uyw4BMUTPHjxAwXiWtFCf... woff2 swap
Size 3 KB
Load time 36 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh50XSwaPGQ3... woff2 swap
Size 3 KB
Load time 33 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh6UVSwaPGQ3... woff2 swap
Size 3 KB
Load time 25 ms
Start 1.0 s
Risk FOUT — text flashes from fallback to web font
S6u9w4BMUTPHh7USSwaPGQ3... woff2 swap
Size 3 KB
Load time 22 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/geometry.js | 3 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.
Network Waterfall52 requests over 2438msINFO
Network Waterfall
52 requests over 2438ms
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.