Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.

SCORE

GRADE

FIX

REVIEW

PASS

INFO

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop

Performance

Accessibility

100

Best Practices

100

SEO

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

1.45 s

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

6.02 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.

0.051

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

2.27 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.

6.03 s

Page Load Progression

385 ms

769 ms

1.2 s

1.5 s

1.9 s

2.3 s

2.7 s

3.1 s

Checks

5 PASS 3 REVIEW 5 FIX

Page Weight Budget

Action

5.8 MB transferred, 85 requests

FIX

5.8 MB transferred, 85 requests

Page weighs 5.9 MB (5.8 MB transferred)

JavaScript is 2.9 MB — consider code splitting or lazy loading

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Got: 2.9 MB

Images are 2.1 MB — compress or use modern formats

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Got: 2.1 MB

Fonts are 373 KB — consider subsetting or using system fonts

Subset fonts to include only used characters, or switch to system font stacks.

Got: 373 KB

CSS is 364 KB — consider purging unused styles

Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.

Got: 364 KB

85 HTTP requests

Estimated 1.2 g CO2 per page load

5.8 MB transferred

85 requests

1.2 g CO2 per page load

JavaScript 2.9 MiB 50%

Images 2.1 MiB 37%

Fonts 373.0 KiB 6%

CSS 364.3 KiB 6%

Other 34.2 KiB 1%

HTML 26.4 KiB 0%

Other 5.2 KiB 0%

Other 2.3 KiB 0%

Other 235 B 0%

0 2.4 MB 4.9 MB

Over budget

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

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

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.

Why this matters

CSS bundle is large — purge unused styles (PurgeCSS, Tailwind JIT) to reduce CSS payload.

Source: web.dev

Third-Party Impact

Action

100% third-party, 0 ms blocking

FIX

100% third-party, 0 ms blocking

Third-party code accounts for 100% of page weight (5.8 MiB of 5.8 MiB)

Third-party blocking time is low (0 ms)

100%

First-party Third-party

JS Bundles

Action

48 scripts, 576 KB unused

FIX

48 scripts, 576 KB unused

https://www.belastingdienst.nl/bld-assets/bld/webc...: 108 KB unused (92%)