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.
4.20 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
4.83 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
2.12 s
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.241
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
7.02 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.
20.55 s
Page Load Progression
DPage Weight BudgetAction2.1 MB transferred, 92 requestsFIX
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
FJS Execution CostAction9079ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.nrc.nl/ | 3846ms | 83ms | 7ms | 3rd |
| https://load.sst.nrc.nl/kxlupzzx.js?st=KKRPPB | 1517ms | 1353ms | 98ms | 3rd |
| https://assets.nrc.nl/static/front/js/main.db164c9ed.js | 846ms | 484ms | 86ms | 3rd |
| Unattributable | 725ms | 23ms | 0ms | 3rd |
| https://load.sst.nrc.nl/gtag/js?id=G-Q3L8E2PF4V&cx=c>m=4e64k0 | 518ms | 406ms | 69ms | 3rd |
| https://prod-nrcm.mhtr.be/public/tr/tracker.min.js | 311ms | 180ms | 96ms | 3rd |
| https://sdk.privacy-center.org/sdk/22ecd6bfac93de604efec0b75b2c796ee1675f92/modern/sdk.22ecd6bfac93de604efec0b75b2c796ee1675f92.js | 255ms | 200ms | 54ms | 3rd |
| https://cdn.sophi.io/assets/demeter/1/stable/3569875221.js?isConsented=true | 230ms | 209ms | 21ms | 3rd |
| https://assets.nrc.nl/static/front/components/js/dmt-icon.2405b9fc1.js | 198ms | 125ms | 53ms | 3rd |
| https://script.hotjar.com/modules.6a0f3932cb1341a35c18.js | 174ms | 143ms | 30ms | 3rd |
Showing top 10 of 14 scripts
DJS BundlesAction23 scripts, 483 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://prod-nrcm.mhtr.be/public/tr/tracker.min.js | 159 KB | 113 KB (71%) | ✓ | 3rd |
| https://assets.nrc.nl/static/front/js/main.db164c9ed.js | 119 KB | 76 KB (65%) | ✓ | 3rd |
| https://sdk.privacy-center.org/sdk/22ecd6bfac93de604efec0b75b2c796ee1675f92/modern/sdk.22ecd6bfac93de604efec0b75b2c796ee1675f92.js | 101 KB | 63 KB (63%) | ✓ | 3rd |
| https://assets.nrc.nl/static/front/components/js/dmt-icon.2405b9fc1.js | 89 KB | 63 KB (71%) | ✓ | 3rd |
| https://load.sst.nrc.nl/gtag/js?id=G-Q3L8E2PF4V&cx=c>m=4e64k0 | 162 KB | 61 KB (38%) | ✓ | 3rd |
| https://load.sst.nrc.nl/kxlupzzx.js?st=KKRPPB | 166 KB | 45 KB (27%) | ✓ | 3rd |
| https://script.hotjar.com/modules.6a0f3932cb1341a35c18.js | 57 KB | 36 KB (64%) | ✓ | 3rd |
| https://assets.nrc.nl/static/front/js/vendor.0677b1b4d.js | 49 KB | 25 KB (50%) | ✓ | 3rd |
| https://assets.nrc.nl/static/front/nmt-split-css-manifest.167c5b347.js | 2 KB | — | ✓ | 3rd |
| https://assets.nrc.nl/static/front/js/chunks/WebNotifications.cffe1920a.js | 1 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
FPage Weight InventoryAction92 resources · 2.1 MB · 483 KB savings availableFIX
~483.0 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 92 resources | 2.1 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BImage Optimization33 images, 0 KB saveableREVIEW
A+Text CompressionAll text resources are compressedPASS
A+Font Loading7 fonts (239 KB)PASS
Web fonts
7
239 KB total
Render-blocking
0
of 7
Dominant font-display
swap
Most common across fonts
Font loading timeline
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 Hints7 hints, 0 missing preconnectsPASS
Current Resource Hints
7 resource hints configured
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
A+Third-Party ResourcesNo third-party resources detectedPASS
A+Green HostingWhether the site is served from green-energy infrastructurePASS
Green Hosting
This site is hosted on green energy infrastructure
Provider: Intermax
Network Waterfall92 requests over 7066msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.nrc.nl www.nrc.nl | Other | 3846ms | 58 KB | — | €42/mo | Costly |
load.sst.nrc.nl load.sst.nrc.nl | Other | 1517ms | 166 KB | 27% | €16/mo | Costly |
assets.nrc.nl assets.nrc.nl | Other | 846ms | 119 KB | 65% | €9/mo | Costly |
Unattributable Unattributable | Other | 725ms | 0 KB | — | €8/mo | Costly |
load.sst.nrc.nl load.sst.nrc.nl | Other | 518ms | 162 KB | 38% | €6/mo | Costly |
prod-nrcm.mhtr.be prod-nrcm.mhtr.be | Other | 311ms | 159 KB | 71% | €3/mo | Costly |
sdk.privacy-center.org sdk.privacy-center.org | Other | 255ms | 101 KB | 63% | €3/mo | Costly |
cdn.sophi.io cdn.sophi.io | Other | 230ms | 41 KB | — | €2/mo | Costly |
assets.nrc.nl assets.nrc.nl | Other | 198ms | 89 KB | 71% | €2/mo | Optional |
Hotjar script.hotjar.com | Session Replay | 174ms | 57 KB | 64% | €2/mo | Optional |
assets.nrc.nl assets.nrc.nl | Other | 171ms | 49 KB | 50% | €2/mo | Optional |
static.chartbeat.com static.chartbeat.com | Other | 100ms | 16 KB | — | €1/mo | Optional |
cdn.parsely.com cdn.parsely.com | Other | 96ms | 21 KB | — | €1/mo | Optional |
static.chartbeat.com static.chartbeat.com | Other | 92ms | 10 KB | — | €1/mo | Optional |
These scripts may cost more than they're worth
- www.nrc.nl adds 3846ms and costs ~€42/month
- load.sst.nrc.nl adds 1517ms and costs ~€16/month
- assets.nrc.nl adds 846ms and costs ~€9/month
- Unattributable adds 725ms and costs ~€8/month
- load.sst.nrc.nl adds 518ms and costs ~€6/month
- prod-nrcm.mhtr.be adds 311ms and costs ~€3/month
- sdk.privacy-center.org adds 255ms and costs ~€3/month
- cdn.sophi.io adds 230ms and costs ~€2/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.nrc.nl takes 3846ms 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
load.sst.nrc.nl takes 1517ms 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.nrc.nl takes 846ms 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
65% of assets.nrc.nl'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
Unattributable takes 725ms 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
load.sst.nrc.nl takes 518ms 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
prod-nrcm.mhtr.be 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
71% of prod-nrcm.mhtr.be'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
sdk.privacy-center.org takes 255ms 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 sdk.privacy-center.org'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
cdn.sophi.io takes 230ms 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
71% of assets.nrc.nl'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
64% of Hotjar'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
50% of assets.nrc.nl'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