Performance
· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.Performance-focused optimization plan with CWV assessment, top offenders, and time estimates
First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.
3.48 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
15.23 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
714 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.036
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
5.68 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.
17.45 s
Page Load Progression
FPage Weight BudgetAction3.1 MB transferred, 43 requestsFIX
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
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.
JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.
Source: web.dev
Subset fonts to include only used characters, or switch to system font stacks.
Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).
Source: web.dev font loading
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
DJS Execution CostAction2362ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.muni.cz/ | 463ms | 106ms | 6ms | 3rd |
| Unattributable | 327ms | 18ms | 0ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-5LQKVJ | 311ms | 256ms | 50ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-DEY88JHR1N&cx=c>m=4e64k0h1 | 300ms | 241ms | 58ms | 3rd |
| https://cdn.muni.cz/css/MuniWeb/_Shared/muniweb.3b230ca2cb814a440239.js | 254ms | 112ms | 44ms | 3rd |
| https://scripts.clarity.ms/0.8.59/clarity.js | 238ms | 207ms | 11ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-000000000&cx=c>m=4e64k0h1 | 209ms | 165ms | 43ms | 3rd |
| https://connect.facebook.net/en_US/fbevents.js | 155ms | 116ms | 38ms | 3rd |
| https://c.seznam.cz/js/rc.js | 104ms | 83ms | 18ms | 3rd |
DJS BundlesAction11 scripts, 353 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://cdn.muni.cz/css/MuniWeb/_Shared/muniweb.3b230ca2cb814a440239.js | 111 KB | 81 KB (73%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-DEY88JHR1N&cx=c>m=4e64k0h1 | 168 KB | 68 KB (40%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-5LQKVJ | 155 KB | 67 KB (43%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-000000000&cx=c>m=4e64k0h1 | 134 KB | 65 KB (48%) | ✓ | 3rd |
| https://connect.facebook.net/en_US/fbevents.js | 99 KB | 44 KB (46%) | ✓ | 3rd |
| https://c.seznam.cz/js/rc.js | 47 KB | 29 KB (63%) | ✓ | 3rd |
| https://analytics.ics.muni.cz:3500/matomo.js | 22 KB | — | ✓ | 3rd |
| https://cdn.muni.cz/Scripts/libs/muni-cookies/main.js | 5 KB | — | ✓ | 3rd |
| https://www.clarity.ms/tag/ku57fhseug | 1 KB | — | ✓ | 3rd |
| https://scripts.clarity.ms/0.8.59/clarity.js | 26 KB | — | ✓ | 3rd |
Consider code splitting or tree shaking to reduce unused code.
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.
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.
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.
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.
This bundle has high unused code — code-split or tree-shake to ship only what executes.
Source: web.dev / Lighthouse coverage
DPage Weight InventoryAction43 resources · 3.1 MB · 353 KB savings availableFIX
~353.5 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 43 resources | 3.1 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CImage OptimizationAction17 images, 0 KB saveableREVIEW
Set explicit width and height to prevent CLS.
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.
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.
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.
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.
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.
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.
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
No green hosting detected
A+Text CompressionAll text resources are compressedPASS
A+Font Loading4 fonts (302 KB)PASS
Web fonts
4
302 KB total
Render-blocking
0
of 4
Dominant font-display
swap
Most common across fonts
Font loading timeline
- Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
- 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 ~132 KB and ~264 ms
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
A+Third-Party ResourcesNo third-party resources detectedPASS
Network Waterfall43 requests over 2238msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.muni.cz www.muni.cz | Other | 463ms | 22 KB | — | Kč57/mo | Costly |
Unattributable Unattributable | Other | 327ms | 0 KB | — | Kč40/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 311ms | 155 KB | 43% | Kč38/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 300ms | 168 KB | 40% | Kč37/mo | Costly |
cdn.muni.cz cdn.muni.cz | Other | 254ms | 111 KB | 73% | Kč31/mo | Costly |
Microsoft Clarity scripts.clarity.ms | Session Replay | 238ms | 26 KB | — | Kč29/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 209ms | 134 KB | 48% | Kč26/mo | Costly |
Facebook Pixel connect.facebook.net | Advertising | 155ms | 99 KB | 46% | Kč19/mo | Optional |
c.seznam.cz c.seznam.cz | Other | 104ms | 47 KB | 63% | Kč13/mo | Optional |
These scripts may cost more than they're worth
- www.muni.cz adds 463ms and costs ~Kč57/month
- Unattributable adds 327ms and costs ~Kč40/month
- Google Tag Manager adds 311ms and costs ~Kč38/month
- Google Tag Manager adds 300ms and costs ~Kč37/month
- cdn.muni.cz adds 254ms and costs ~Kč31/month
- Microsoft Clarity adds 238ms and costs ~Kč29/month
- Google Tag Manager adds 209ms and costs ~Kč26/month
100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.
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
www.muni.cz takes 463ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
Unattributable takes 327ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
Google Tag Manager takes 311ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
Google Tag Manager takes 300ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
cdn.muni.cz takes 254ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
73% of cdn.muni.cz's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
Microsoft Clarity takes 238ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
Google Tag Manager takes 209ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
63% of c.seznam.cz's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev