Performance
· 15 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.
999 ms
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
3.80 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
225 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.057
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
1.72 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.
3.92 s
Page Load Progression
FPage Weight BudgetAction4.7 MB transferred, 111 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
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.
Source: web.dev
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
DPage Weight InventoryAction111 resources · 4.7 MB · 210 KB savings availableFIX
~209.6 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 111 resources | 4.7 MiB | ||||||
BImage Optimization33 images, 0 KB saveableREVIEW
CJS Execution CostAction1700ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.vrt.be/nl/_next/static/chunks/788-2886a49e9b3c002a.js | 472ms | 326ms | 19ms | 3rd |
| https://www.vrt.be/nl | 400ms | 18ms | 14ms | 3rd |
| Unattributable | 326ms | 13ms | 0ms | 3rd |
| https://assets.adobedtm.com/launch-EN7e1ba6190f45421f81025c684b630cc1.min.js | 237ms | 193ms | 28ms | 3rd |
| https://www.vrt.be/nl/_next/static/chunks/webpack-kFIv2lOFM5wBTJk0jqFxM.js | 156ms | 144ms | 11ms | 3rd |
| https://cmp-sp.vrt.be/unified/wrapperMessagingWithoutDetection.js | 109ms | 100ms | 4ms | 3rd |
CJS BundlesAction41 scripts, 210 KB unusedREVIEW
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.vrt.be/nl/_next/static/chunks/7236-c9a0814d0fa8c7de.js | 106 KB | 92 KB (88%) | ✓ | 3rd |
| https://www.vrt.be/nl/_next/static/chunks/788-2886a49e9b3c002a.js | 108 KB | 41 KB (38%) | ✓ | 3rd |
| https://www.vrt.be/nl/_next/static/chunks/2441-611017b1de707d48.js | 36 KB | 29 KB (84%) | ✓ | 3rd |
| https://assets.adobedtm.com/launch-EN7e1ba6190f45421f81025c684b630cc1.min.js | 111 KB | 27 KB (34%) | ✓ | 3rd |
| https://www.vrt.be/nl/_next/static/chunks/8318-e576da1540faeb60.js | 30 KB | 21 KB (71%) | ✓ | 3rd |
| https://www.vrt.be/nl/_next/static/chunks/6748-519fd04ae01b0e61.js | 4 KB | — | ✓ | 3rd |
| https://assets.adobedtm.com/extensions/EP171e731c9ba34f1c950c36d26e3efd61/AppMeasurement.min.js | 12 KB | — | ✓ | 3rd |
| https://www.vrt.be/nl/_next/static/chunks/main-app-502768519311bd92.js | 2 KB | — | ✓ | 3rd |
| https://www.vrt.be/nl/_next/static/chunks/app/global-error-725c14999bb62379.js | 4 KB | — | ✓ | 3rd |
| https://www.vrt.be/nl/_next/static/chunks/9894-e336c31053099c28.js | 10 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
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 Loading5 fonts (129 KB)PASS
Web fonts
5
129 KB total
Render-blocking
0
of 5
Dominant font-display
swap
Most common across fonts
Font loading timeline
- Convert to woff2 for ~30% smaller file size
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 CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
AHTTP Cachingmax-age=300 (5 minutes)PASS
public, max-age=300
| Directive | Value | Meaning |
|---|---|---|
| public | — | Any cache may store this response |
| max-age | 300 | Cache for 5 minutes |
Network Waterfall111 requests over 5178msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.vrt.be www.vrt.be | Other | 472ms | 108 KB | 38% | €5/mo | Costly |
www.vrt.be www.vrt.be | Other | 400ms | 72 KB | — | €4/mo | Costly |
Unattributable Unattributable | Other | 326ms | 0 KB | — | €4/mo | Costly |
assets.adobedtm.com assets.adobedtm.com | Other | 237ms | 111 KB | 34% | €3/mo | Costly |
www.vrt.be www.vrt.be | Other | 156ms | 4 KB | — | €2/mo | Optional |
cmp-sp.vrt.be cmp-sp.vrt.be | Other | 109ms | 40 KB | — | €1/mo | Optional |
These scripts may cost more than they're worth
- www.vrt.be adds 472ms and costs ~€5/month
- www.vrt.be adds 400ms and costs ~€4/month
- Unattributable adds 326ms and costs ~€4/month
- assets.adobedtm.com adds 237ms and costs ~€3/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.vrt.be takes 472ms 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
www.vrt.be takes 400ms 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 326ms 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
assets.adobedtm.com takes 237ms 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