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https://www.gov.uk

Performance

· 26 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
97
GRADE
A+
FIX
0
REVIEW
3
PASS
19
INFO
4

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

Mobile Desktop
98
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
100
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
100
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

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

1.80 s

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

1.84 s

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

14 ms

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

0.000

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

1.80 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.

1.84 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
26
19 PASS 3 REVIEW
B
Image Optimization
4 images, 0 KB saveable
REVIEW
4 images, 0 KB saveable
Info::
All images are well-optimized
4 images 18 KB
0 oversized -0 KB
4 legacy format
0 missing dimensions CLS risk
C
Compression Algorithm
Action
Main response served uncompressed
REVIEW
Main response served uncompressed
Info::
Main HTML response has no Content-Encoding (uncompressed)
The main HTML document is served without compression. The Text Compression section above lists the broader picture; for the main response specifically, even gzip would shave ~70-80% off most text payloads.
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Page Weight Budget
191 KB transferred, 15 requests
PASS
191 KB transferred, 15 requests
Info::
Page weighs 744 KB (191 KB transferred)
Info::
15 HTTP requests
Info::
Estimated 0.04 g CO2 per page load
191 KB / 2.4 MB budget
191 KB transferred
15 requests
0.04 g CO2 per page load
Fonts 64.1 KiB 34%
JavaScript 55.3 KiB 29%
CSS 38.7 KiB 20%
Images 18.3 KiB 10%
HTML 13.3 KiB 7%
Other 1.2 KiB 1%
0 2.4 MB 4.9 MB
Under budget
A+
Third-Party Impact
No third-party resources
PASS
No third-party resources
Info::
No third-party resources detected
No third-party resources detected — all resources are first-party.
A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
JS Execution Cost
438ms total JS execution
PASS
438ms total JS execution
Info::
https://www.gov.uk/: 193ms CPU time
Info::
Unattributable: 143ms CPU time
Info::
https://www.gov.uk/assets/frontend/application-1a5...: 101ms CPU time
Info::
Third-party scripts: 143ms (33% of total)

Main Thread Breakdown

Other 39% Style & Layout 27% Script Evaluation 23% Parse HTML & CSS 6% Rendering 5%
ScriptTotalScriptingParse/CompileParty
https://www.gov.uk/193ms8ms1ms1st
Unattributable143ms8ms0ms3rd
https://www.gov.uk/assets/frontend/application-1a5599d4d125638383132e6e2357b6929a56b9cab8cfb0a71a17386e0809dcff.js101ms83ms0ms1st
A+
Font Loading
2 fonts (64 KB)
PASS
2 fonts (64 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

64 KB total

Render-blocking

0

of 2

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s 1.5 s FCP 1.8 s LCP 1.8 shttps://www.gov.uk/assets/frontend/bold-b542beb274-v2-35bf540bb39615b6a517986f3aa83f7fefa1efd1878603eeeb196488078542d1.woff2bold-b542beb274-v2-35bf... https://www.gov.uk/assets/frontend/bold-b542beb274-v2-35bf540bb39615b6a517986f3aa83f7fefa1efd1878603eeeb196488078542d1.woff2 — 31.1 KiB — 5 ms — font-display: swaphttps://www.gov.uk/assets/frontend/light-94a07e06a1-v2-01565b0034e61d4609689bbb7ae0be844701f3812c8fe029fa1659b7ef3aa94f.woff2light-94a07e06a1-v2-015... https://www.gov.uk/assets/frontend/light-94a07e06a1-v2-01565b0034e61d4609689bbb7ae0be844701f3812c8fe029fa1659b7ef3aa94f.woff2 — 33.0 KiB — 5 ms — font-display: swap
bold-b542beb274-v2-35bf... woff2 swap
Size 31 KB
Load time 5 ms
Start 166 ms
Risk FOUT — text flashes from fallback to web font
light-94a07e06a1-v2-015... woff2 swap
Size 33 KB
Load time 5 ms
Start 166 ms
Risk FOUT — text flashes from fallback to web font
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+
JS Bundles
5 scripts, 26 KB unused
PASS
5 scripts, 26 KB unused
Warning::
https://www.gov.uk/assets/frontend/application-1a5...: 26 KB unused (64%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 26 KB
26 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.gov.uk/assets/frontend/application-1a5599d4d125638383132e6e2357b6929a56b9cab8cfb0a71a17386e0809dcff.js41 KB26 KB (64%)✓1st
https://www.gov.uk/assets/frontend/govuk_publishing_components/vendor/lux/lux-measurer-d66192b1b665d415e1874e49a48138b7ae339548aa6cdb8687c7f9933e72b969.js1 KB—✓1st
https://www.gov.uk/assets/frontend/govuk_publishing_components/rum-custom-data-b9e1806d1da2fa8ef1855d01aa71ba5eb0afc010dd2c4de3672cc7c7a39b0c8c.js1 KB—✓1st
https://www.gov.uk/assets/frontend/govuk_publishing_components/rum-loader-a65b10e18ceeba3bd8a2eac507c7f2c513cdc82f35097df903fdea87f1dc2e33.js1 KB—✓1st
https://www.gov.uk/assets/frontend/govuk_publishing_components/load-analytics-884d892f2ad6c2e83d4c1b5e60dfb334fa20bf05a057bdbbc843ac3fa45a696d.js12 KB—✓1st

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
A+
HTTP/3 (QUIC)
HTTP/3 advertised via Alt-Svc
PASS
HTTP/3 advertised via Alt-Svc
Info::
HTTP/3 (QUIC) is supported
First-load mobile users on cellular networks see meaningful latency improvements with HTTP/3. The QUIC transport collapses TLS + TCP handshakes into one and recovers faster from packet loss.
A+
LCP Image Preload
LCP preload audit not available
PASS
LCP preload audit not available
Info::
LCP image preload audit not available for this scan
A+
Main HTML Cache-Control
Main HTML max-age=300 (≤ 5min) is appropriate
PASS
Main HTML max-age=300 (≤ 5min) is appropriate
Info::
Main HTML max-age=300 (≤ 5min) is appropriate
Got: max-age=300, public
A+
Server-Timing Observability
1 Server-Timing entries advertised
PASS
1 Server-Timing entries advertised
Info::
Server-Timing header advertises 1 timing entries
A+
Page Weight Inventory
15 resources · 191 KB · 26 KB savings available
PASS
15 resources · 191 KB · 26 KB savings available
Info::
Within 1MB page-weight target
Got: 191 KB
15 resources · 190.8 KiB · 0 third-party Within 1MB page-weight target
Font 34% · 64.1 KiB
JavaScript 29% · 55.3 KiB
CSS 20% · 38.7 KiB
Image 10% · 19.5 KiB
Document 7% · 13.3 KiB

~26.2 KiB of savings available

Remove unused JavaScript: 26.2 KiB
A+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
No render-blocking resources detected in <head>
A+
Third-Party Resources
No third-party resources detected
PASS
No third-party resources detected
A+
JavaScript Blocking
No render-blocking JS or document.write usage detected
PASS
No render-blocking JS or document.write usage detected
Info::
No JavaScript blocking issues detected
A+
CSS Performance Depth
No CSS performance depth issues detected
PASS
No CSS performance depth issues detected
Info::
No CSS performance depth issues detected
A+
HTTP Caching
max-age=300 (5 minutes)
PASS
max-age=300 (5 minutes)
Info::
Cache-Control header is set
Got: max-age=300, public
Info::
Effective TTL: 5 minutes (max-age=300)
Info::
ETag present — enables conditional (304) responses
Cache-Control

max-age=300, public

DirectiveValueMeaning
max-age300Cache for 5 minutes
public—Any cache may store this response
Effective TTL: 300 seconds
Network Waterfall
15 requests over 190ms
INFO
0 ms 500 ms 1.0 s 1.5 s FCP 1.8 s LCP 1.8 shttps://www.gov.uk// https://www.gov.uk/ — 200 — 13.3 KiB — 78 ms — h2https://www.gov.uk/assets/frontend/views/_homepage-64a9f4f542bbda5bcdae1df09ea442583c3981460eb5cd3be12e18ba1885ba31.css/assets/frontend/views/_homepage-64... https://www.gov.uk/assets/frontend/views/_homepage-64a9f4f542bbda5bcdae1df09ea442583c3981460eb5cd3be12e18ba1885ba31.css — 200 — 1.6 KiB — 3 ms — h2https://www.gov.uk/assets/frontend/govuk_publishing_components/vendor/lux/lux-measurer-d66192b1b665d415e1874e49a48138b7ae339548aa6cdb8687c7f9933e72b969.js/assets/frontend/govuk_publishing_c... https://www.gov.uk/assets/frontend/govuk_publishing_components/vendor/lux/lux-measurer-d66192b1b665d415e1874e49a48138b7ae339548aa6cdb8687c7f9933e72b969.js — 200 — 833 B — 3 ms — h2https://www.gov.uk/assets/frontend/govuk_publishing_components/rum-custom-data-b9e1806d1da2fa8ef1855d01aa71ba5eb0afc010dd2c4de3672cc7c7a39b0c8c.js/assets/frontend/govuk_publishing_c... https://www.gov.uk/assets/frontend/govuk_publishing_components/rum-custom-data-b9e1806d1da2fa8ef1855d01aa71ba5eb0afc010dd2c4de3672cc7c7a39b0c8c.js — 200 — 571 B — 9 ms — h3https://www.gov.uk/assets/frontend/govuk_publishing_components/rum-loader-a65b10e18ceeba3bd8a2eac507c7f2c513cdc82f35097df903fdea87f1dc2e33.js/assets/frontend/govuk_publishing_c... https://www.gov.uk/assets/frontend/govuk_publishing_components/rum-loader-a65b10e18ceeba3bd8a2eac507c7f2c513cdc82f35097df903fdea87f1dc2e33.js — 200 — 709 B — 9 ms — h3https://www.gov.uk/assets/frontend/govuk_publishing_components/load-analytics-884d892f2ad6c2e83d4c1b5e60dfb334fa20bf05a057bdbbc843ac3fa45a696d.js/assets/frontend/govuk_publishing_c... https://www.gov.uk/assets/frontend/govuk_publishing_components/load-analytics-884d892f2ad6c2e83d4c1b5e60dfb334fa20bf05a057bdbbc843ac3fa45a696d.js — 200 — 12.1 KiB — 9 ms — h3https://www.gov.uk/assets/frontend/application-2a99308fa11f10b8f02cc0c1740e2f3f6add28c5e121cc679916b911bd8741f3.css/assets/frontend/application-2a9930... https://www.gov.uk/assets/frontend/application-2a99308fa11f10b8f02cc0c1740e2f3f6add28c5e121cc679916b911bd8741f3.css — 200 — 37.1 KiB — 9 ms — h3https://www.gov.uk/assets/frontend/application-1a5599d4d125638383132e6e2357b6929a56b9cab8cfb0a71a17386e0809dcff.js/assets/frontend/application-1a5599... https://www.gov.uk/assets/frontend/application-1a5599d4d125638383132e6e2357b6929a56b9cab8cfb0a71a17386e0809dcff.js — 200 — 41.1 KiB — 10 ms — h3https://www.gov.uk/assets/frontend/govuk_publishing_components/icon-close-eecb5fdf67d1688ddf2f93e6e09d5f87b9b24e0fc53596ad2a65cf187c2c7c76.svg/assets/frontend/govuk_publishing_c... https://www.gov.uk/assets/frontend/govuk_publishing_components/icon-close-eecb5fdf67d1688ddf2f93e6e09d5f87b9b24e0fc53596ad2a65cf187c2c7c76.svg — 200 — 515 B — 3 ms — h3https://www.gov.uk/assets/frontend/govuk-crest-9f82a3631d8ac5feb4660345a2b44ca98f077b48248f2cc139a0f412355bebef.svg/assets/frontend/govuk-crest-9f82a3... https://www.gov.uk/assets/frontend/govuk-crest-9f82a3631d8ac5feb4660345a2b44ca98f077b48248f2cc139a0f412355bebef.svg — 200 — 14.6 KiB — 3 ms — h3https://www.gov.uk/assets/frontend/bold-b542beb274-v2-35bf540bb39615b6a517986f3aa83f7fefa1efd1878603eeeb196488078542d1.woff2/assets/frontend/bold-b542beb274-v2... https://www.gov.uk/assets/frontend/bold-b542beb274-v2-35bf540bb39615b6a517986f3aa83f7fefa1efd1878603eeeb196488078542d1.woff2 — 200 — 31.1 KiB — 5 ms — h3https://www.gov.uk/assets/frontend/light-94a07e06a1-v2-01565b0034e61d4609689bbb7ae0be844701f3812c8fe029fa1659b7ef3aa94f.woff2/assets/frontend/light-94a07e06a1-v... https://www.gov.uk/assets/frontend/light-94a07e06a1-v2-01565b0034e61d4609689bbb7ae0be844701f3812c8fe029fa1659b7ef3aa94f.woff2 — 200 — 33.0 KiB — 5 ms — h3https://www.gov.uk/assets/frontend/homepage/find-a-job-4d38717b0451da3bb223ddea7f681d79e48c1c022da5a08f16aba3f681503150.png/assets/frontend/homepage/find-a-jo... https://www.gov.uk/assets/frontend/homepage/find-a-job-4d38717b0451da3bb223ddea7f681d79e48c1c022da5a08f16aba3f681503150.png — 200 — 1.7 KiB — 2 ms — h3https://www.gov.uk/assets/frontend/homepage/national-insurance-featured-7169e3631b639dcfc7be22469daf155ad0aa7516143ff8cf2e6f95ba29c8656c.png/assets/frontend/homepage/national-... https://www.gov.uk/assets/frontend/homepage/national-insurance-featured-7169e3631b639dcfc7be22469daf155ad0aa7516143ff8cf2e6f95ba29c8656c.png — 200 — 1.5 KiB — 2 ms — h3https://www.gov.uk/assets/frontend/favicon-d962d21b5bb443f546c097ea21b567cde639adef7370da45be5e349ba8d62d33.svg/assets/frontend/favicon-d962d21b5b... https://www.gov.uk/assets/frontend/favicon-d962d21b5bb443f546c097ea21b567cde639adef7370da45be5e349ba8d62d33.svg — 200 — 1.2 KiB — 2 ms — h3
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
33% of JavaScript execution is third-party
First-party Third-party 143ms · 0KB · £1/mo
Unattributable
Other
Optional
Execution 143ms
Transfer 0 KB
Monthly Cost £1/mo

How third-party costs are calculated

Real-User Performance (CrUX)
Field metrics from the Chrome User Experience Report
INFO

Chrome User Experience (CrUX)

Real-user metrics from the Chrome UX Report (2026-04-10 — 2026-05-07)

LCP (p75)

660 ms

97% good

INP (p75)

95 ms

94% good

CLS (p75)

0.000

94% good

FCP (p75)

600 ms

TTFB (p75)

259 ms

This origin passes Core Web Vitals assessment
Image Optimization
4 images, 8 KB total, 7 KB wasted
INFO

Image Optimization Audit

Total Images

4

Total Size

8 KB

Oversized

4

Wasted

7 KB

4 missing alt text
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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