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

100

Accessibility

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.

704 ms

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

1.14 s

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

2 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.199

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

704 ms

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

1.59 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 s

Checks

7 PASS 4 REVIEW 2 FIX

Third-Party Impact

Action

62% third-party, 0 ms blocking

FIX

62% third-party, 0 ms blocking

Third-party code accounts for 62% of page weight (742.7 KiB of 1.2 MiB)

Third-party blocking time is low (0 ms)

38%

62%

First-party Third-party

HTTP Caching

Action

No cache headers

FIX

No cache headers

No Cache-Control header found

Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

Page Weight Budget

1.2 MB transferred, 36 requests

REVIEW

1.2 MB transferred, 36 requests

Page weighs 2.6 MB (1.2 MB transferred)

JavaScript is 534 KB — consider code splitting or lazy loading

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

Got: 534 KB

36 HTTP requests

Estimated 0.25 g CO2 per page load

1.2 MB transferred

36 requests

0.25 g CO2 per page load

JavaScript 534.3 KiB 44%

Images 384.7 KiB 32%

CSS 186.5 KiB 16%

Fonts 70.4 KiB 6%

HTML 17.8 KiB 1%

Other 5.2 KiB 0%

Other 1.2 KiB 0%

Other 606 B 0%

0 2.4 MB 4.9 MB

Under 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

Image Optimization

Action

14 images, 0 KB saveable

REVIEW

14 images, 0 KB saveable

https://commonslibrary.parliament.uk/content/theme... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://commonslibrary.parliament.uk/content/theme... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

https://commonslibrary.parliament.uk/content/theme... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

14 images 385 KB

0 oversized -0 KB

13 legacy format

3 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

JS Bundles

Action

10 scripts, 221 KB unused

REVIEW

10 scripts, 221 KB unused

https://www.googletagmanager.com/gtag/js?id=G-9684...: 66 KB unused (42%)