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https://hse.gov.uk

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
86
GRADE
B
FIX
2
REVIEW
4
PASS
9
INFO
2

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

Mobile Desktop
37
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.

6.06 s

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

11.33 s

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

94 ms

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

0.549

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

6.06 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.

11.33 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
17
9 PASS 4 REVIEW 2 FIX
D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (783.3 KiB of 783.4 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
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.

C
Image Optimization
Action
9 images, 0 KB saveable
REVIEW
9 images, 0 KB saveable
Warning::
https://www.hse.gov.uk/assets/homepage/images/sara... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.hse.gov.uk/assets/homepage/images/sara... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.hse.gov.uk/assets/homepage/images/miss... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.hse.gov.uk/assets/homepage/images/care... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
9 images 280 KB
0 oversized -0 KB
8 legacy format
4 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

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

B
JS Execution Cost
742ms total JS execution
REVIEW
742ms total JS execution
Info::
https://www.hse.gov.uk/: 193ms CPU time
Info::
https://www.hse.gov.uk/assets/v6-js/cookies-6.6.0....: 161ms CPU time
Info::
Unattributable: 160ms CPU time
Info::
https://www.hse.gov.uk/assets/v6-js/main-6.6.0.min...: 146ms CPU time
Info::
https://cse.google.com/cse.js?cx=01584817831528903...: 83ms CPU time
Warning::
Third-party scripts: 742ms (100% of total)

Main Thread Breakdown

Script Evaluation 48% Other 22% Style & Layout 13% Script Parsing & Compilation 11% Parse HTML & CSS 3%
ScriptTotalScriptingParse/CompileParty
https://www.hse.gov.uk/193ms11ms2ms3rd
https://www.hse.gov.uk/assets/v6-js/cookies-6.6.0.js161ms139ms20ms3rd
Unattributable160ms8ms0ms3rd
https://www.hse.gov.uk/assets/v6-js/main-6.6.0.min.js146ms109ms32ms3rd
https://cse.google.com/cse.js?cx=015848178315289032903:hqkynptgd1o83ms73ms1ms3rd
C
JS Bundles
Action
9 scripts, 188 KB unused
REVIEW
9 scripts, 188 KB unused
Warning::
https://www.hse.gov.uk/assets/v6-js/main-6.6.0.min...: 73 KB unused (60%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.google.com/cse/static/element/b33cba58...: 48 KB unused (49%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.hse.gov.uk/assets/v6-js/cookies-6.6.0....: 35 KB unused (45%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cse.google.com/adsense/search/async-ads.js: 32 KB unused (73%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 188 KB
188 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.hse.gov.uk/assets/v6-js/main-6.6.0.min.js122 KB73 KB (60%)✓3rd
https://www.google.com/cse/static/element/b33cba5881f68fbf/cse_element__en.js?usqp=CAI%3D98 KB48 KB (49%)✓3rd
https://www.hse.gov.uk/assets/v6-js/cookies-6.6.0.js79 KB35 KB (45%)✓3rd
https://cse.google.com/adsense/search/async-ads.js44 KB32 KB (73%)✓3rd
https://analytics.silktide.com/0a7782bc3e87b8c10c781f3dee43fde7.js16 KB—✓3rd
https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da177152312451611 KB—✓3rd
https://cse.google.com/cse.js?cx=015848178315289032903:hqkynptgd1o4 KB—✓3rd
https://ep2.adtrafficquality.google/sodar/sodar2.js8 KB—✓3rd
https://pagead2.googlesyndication.com/bg/dj12lhpBI2WR1GQ6n5lcmp69XlpHOiTAWO7c9b6NTo0.js22 KB—✓3rd

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

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

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

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

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A
Page Weight Budget
783 KB transferred, 31 requests
PASS
783 KB transferred, 31 requests
Info::
Page weighs 1.9 MB (783 KB transferred)
Info::
31 HTTP requests
Info::
Estimated 0.16 g CO2 per page load
783 KB / 2.4 MB budget
783 KB transferred
31 requests
0.16 g CO2 per page load
JavaScript 402.6 KiB 51%
Images 279.7 KiB 36%
CSS 39.5 KiB 5%
Fonts 36.7 KiB 5%
HTML 16.0 KiB 2%
Other 8.3 KiB 1%
Other 437 B 0%
Other 375 B 0%
0 2.4 MB 4.9 MB
Under budget
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+
Font Loading
1 fonts (37 KB)
PASS
1 fonts (37 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

37 KB total

Render-blocking

0

of 1

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s FCP 6.1 s LCP 11.3 shttps://fonts.gstatic.com/s/roboto/v51/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2KFO7CnqEu92Fr1ME7kSn66a... https://fonts.gstatic.com/s/roboto/v51/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2 — 36.7 KiB — 47 ms — font-display: swap
KFO7CnqEu92Fr1ME7kSn66a... woff2 swap
Size 37 KB
Load time 47 ms
Start 330 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+
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
Page Weight Inventory
31 resources · 783 KB · 188 KB savings available
PASS
31 resources · 783 KB · 188 KB savings available
Info::
Within 1MB page-weight target
Got: 783 KB
Info::
~188 KB of savings available
Warning::
30 third-party resources (100% of weight)
31 resources · 783.4 KiB · 30 third-party Within 1MB page-weight target
JavaScript 51% · 402.6 KiB
Image 36% · 280.0 KiB
CSS 5% · 39.5 KiB
Font 5% · 36.7 KiB
Document 2% · 16.1 KiB
Other 1% · 8.7 KiB

~188.0 KiB of savings available

Remove unused JavaScript: 188.0 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
Network Waterfall
31 requests over 1782ms
INFO
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s FCP 6.1 s LCP 11.3 shttps://hse.gov.uk// https://hse.gov.uk/ — 301 — 100 B — 89 ms — h2https://www.hse.gov.uk/www.hse.gov.uk/ https://www.hse.gov.uk/ — 200 — 10.2 KiB — 89 ms — h2https://www.hse.gov.uk/assets/v6-js/cookies-6.6.0.jswww.hse.gov.uk/assets/v6-js/cookies... https://www.hse.gov.uk/assets/v6-js/cookies-6.6.0.js — 200 — 78.6 KiB — 52 ms — h2https://www.hse.gov.uk/assets/v6-css/6.6.0.min.csswww.hse.gov.uk/assets/v6-css/6.6.0.... https://www.hse.gov.uk/assets/v6-css/6.6.0.min.css — 200 — 24.4 KiB — 75 ms — h2https://fonts.googleapis.com/css?family=Roboto:100,200,300,400,500,600,700,400italic&display=swapfonts.googleapis.com/css?family=Rob... https://fonts.googleapis.com/css?family=Roboto:100,200,300,400,500,600,700,400italic&display=swap — 200 — 2.6 KiB — 97 ms — h2https://www.hse.gov.uk/assets/homepage/images/asbestos-workers-mobile.avifwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/asbestos-workers-mobile.avif — 200 — 44.4 KiB — 60 ms — h2https://www.hse.gov.uk/assets/homepage/images/sarah-albon.jpgwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/sarah-albon.jpg — 200 — 50.5 KiB — 60 ms — h2https://www.hse.gov.uk/assets/homepage/images/sarah-newton.jpgwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/sarah-newton.jpg — 200 — 60.3 KiB — 68 ms — h2https://www.hse.gov.uk/assets/homepage/images/mission.jpgwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/mission.jpg — 200 — 61.8 KiB — 115 ms — h3https://www.hse.gov.uk/assets/homepage/images/careers.jpgwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/careers.jpg — 200 — 59.3 KiB — 111 ms — h3https://www.hse.gov.uk/assets/v6-js/main-6.6.0.min.jswww.hse.gov.uk/assets/v6-js/main-6.... https://www.hse.gov.uk/assets/v6-js/main-6.6.0.min.js — 200 — 121.5 KiB — 88 ms — h3https://analytics.silktide.com/0a7782bc3e87b8c10c781f3dee43fde7.jsanalytics.silktide.com/0a7782bc3e87... https://analytics.silktide.com/0a7782bc3e87b8c10c781f3dee43fde7.js — 200 — 16.4 KiB — 47 ms — h2https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da1771523124516static.cloudflareinsights.com/beaco... https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da1771523124516 — 200 — 10.7 KiB — 95 ms — h2https://fonts.gstatic.com/s/roboto/v51/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2fonts.gstatic.com/s/roboto/v51/KFO7... https://fonts.gstatic.com/s/roboto/v51/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2 — 200 — 36.7 KiB — 47 ms — h3https://www.hse.gov.uk/assets/ajax/global-message.jsonwww.hse.gov.uk/assets/ajax/global-m... https://www.hse.gov.uk/assets/ajax/global-message.json — 200 — 375 B — 37 ms — h3https://cse.google.com/cse.js?cx=015848178315289032903:hqkynptgd1ocse.google.com/cse.js?cx=0158481783... https://cse.google.com/cse.js?cx=015848178315289032903:hqkynptgd1o — 200 — 3.7 KiB — 107 ms — h2https://www.google.com/cse/static/element/b33cba5881f68fbf/cse_element__en.js?usqp=CAI%3Dwww.google.com/cse/static/element/b... https://www.google.com/cse/static/element/b33cba5881f68fbf/cse_element__en.js?usqp=CAI%3D — 200 — 98.5 KiB — 92 ms — h3https://www.google.com/cse/static/element/b33cba5881f68fbf/default_v6+en.csswww.google.com/cse/static/element/b... https://www.google.com/cse/static/element/b33cba5881f68fbf/default_v6+en.css — 200 — 9.7 KiB — 64 ms — h3https://www.google.com/cse/static/style/look/v6/default.csswww.google.com/cse/static/style/loo... https://www.google.com/cse/static/style/look/v6/default.css — 200 — 1.2 KiB — 54 ms — h3https://www.google.com/cse/static/element/b33cba5881f68fbf/mobile_v6+en.csswww.google.com/cse/static/element/b... https://www.google.com/cse/static/element/b33cba5881f68fbf/mobile_v6+en.css — 200 — 1.5 KiB — 23 ms — h3https://cse.google.com/adsense/search/async-ads.jscse.google.com/adsense/search/async... https://cse.google.com/adsense/search/async-ads.js — 200 — 43.6 KiB — 54 ms — h2https://www.google.com/cse/static/images/2x/en/branding.pngwww.google.com/cse/static/images/2x... https://www.google.com/cse/static/images/2x/en/branding.png — 200 — 3.3 KiB — 20 ms — h3https://clients1.google.com/generate_204clients1.google.com/generate_204 https://clients1.google.com/generate_204 — 204 — 117 B — 91 ms — h2https://ep1.adtrafficquality.google/getconfig/sodar?sv=200&tid=afs&tv=1234567890&st=env&sjk=wT4iHElXQ0OkR0MUGqKU2A==&sde=1ep1.adtrafficquality.google/getconf... https://ep1.adtrafficquality.google/getconfig/sodar?sv=200&tid=afs&tv=1234567890&st=env&sjk=wT4iHElXQ0OkR0MUGqKU2A==&sde=1 — 200 — 8.1 KiB — 81 ms — h3https://www.hse.gov.uk/cdn-cgi/rum?www.hse.gov.uk/cdn-cgi/rum? https://www.hse.gov.uk/cdn-cgi/rum? — 204 — 184 B — 21 ms — h3https://www.hse.gov.uk/favicon.icowww.hse.gov.uk/favicon.ico https://www.hse.gov.uk/favicon.ico — 200 — 337 B — 26 ms — h3https://ep2.adtrafficquality.google/sodar/sodar2.jsep2.adtrafficquality.google/sodar/s... https://ep2.adtrafficquality.google/sodar/sodar2.js — 200 — 7.9 KiB — 94 ms — h2https://ep2.adtrafficquality.google/sodar/sodar2/254/runner.htmlep2.adtrafficquality.google/sodar/s... https://ep2.adtrafficquality.google/sodar/sodar2/254/runner.html — 200 — 5.8 KiB — 69 ms — h2https://pagead2.googlesyndication.com/bg/dj12lhpBI2WR1GQ6n5lcmp69XlpHOiTAWO7c9b6NTo0.jspagead2.googlesyndication.com/bg/dj... https://pagead2.googlesyndication.com/bg/dj12lhpBI2WR1GQ6n5lcmp69XlpHOiTAWO7c9b6NTo0.js — 200 — 21.6 KiB — 100 ms — h3https://ep2.adtrafficquality.google/generate_204?L01KIgep2.adtrafficquality.google/generat... https://ep2.adtrafficquality.google/generate_204?L01KIg — 204 — 40 B — 23 ms — h2
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s FCP 6.1 s LCP 11.3 shttps://hse.gov.uk// https://hse.gov.uk/ — 301 — 100 B — 89 ms — h2https://www.hse.gov.uk/www.hse.gov.uk/ https://www.hse.gov.uk/ — 200 — 10.2 KiB — 89 ms — h2https://www.hse.gov.uk/assets/v6-js/cookies-6.6.0.jswww.hse.gov.uk/assets/v6-js/cookies... https://www.hse.gov.uk/assets/v6-js/cookies-6.6.0.js — 200 — 78.6 KiB — 52 ms — h2https://www.hse.gov.uk/assets/v6-css/6.6.0.min.csswww.hse.gov.uk/assets/v6-css/6.6.0.... https://www.hse.gov.uk/assets/v6-css/6.6.0.min.css — 200 — 24.4 KiB — 75 ms — h2https://fonts.googleapis.com/css?family=Roboto:100,200,300,400,500,600,700,400italic&display=swapfonts.googleapis.com/css?family=Rob... https://fonts.googleapis.com/css?family=Roboto:100,200,300,400,500,600,700,400italic&display=swap — 200 — 2.6 KiB — 97 ms — h2https://www.hse.gov.uk/assets/homepage/images/asbestos-workers-mobile.avifwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/asbestos-workers-mobile.avif — 200 — 44.4 KiB — 60 ms — h2https://www.hse.gov.uk/assets/homepage/images/sarah-albon.jpgwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/sarah-albon.jpg — 200 — 50.5 KiB — 60 ms — h2https://www.hse.gov.uk/assets/homepage/images/sarah-newton.jpgwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/sarah-newton.jpg — 200 — 60.3 KiB — 68 ms — h2https://www.hse.gov.uk/assets/homepage/images/mission.jpgwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/mission.jpg — 200 — 61.8 KiB — 115 ms — h3https://www.hse.gov.uk/assets/homepage/images/careers.jpgwww.hse.gov.uk/assets/homepage/imag... https://www.hse.gov.uk/assets/homepage/images/careers.jpg — 200 — 59.3 KiB — 111 ms — h3https://www.hse.gov.uk/assets/v6-js/main-6.6.0.min.jswww.hse.gov.uk/assets/v6-js/main-6.... https://www.hse.gov.uk/assets/v6-js/main-6.6.0.min.js — 200 — 121.5 KiB — 88 ms — h3https://analytics.silktide.com/0a7782bc3e87b8c10c781f3dee43fde7.jsanalytics.silktide.com/0a7782bc3e87... https://analytics.silktide.com/0a7782bc3e87b8c10c781f3dee43fde7.js — 200 — 16.4 KiB — 47 ms — h2https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da1771523124516static.cloudflareinsights.com/beaco... https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da1771523124516 — 200 — 10.7 KiB — 95 ms — h2https://fonts.gstatic.com/s/roboto/v51/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2fonts.gstatic.com/s/roboto/v51/KFO7... https://fonts.gstatic.com/s/roboto/v51/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2 — 200 — 36.7 KiB — 47 ms — h3https://www.hse.gov.uk/assets/ajax/global-message.jsonwww.hse.gov.uk/assets/ajax/global-m... https://www.hse.gov.uk/assets/ajax/global-message.json — 200 — 375 B — 37 ms — h3https://cse.google.com/cse.js?cx=015848178315289032903:hqkynptgd1ocse.google.com/cse.js?cx=0158481783... https://cse.google.com/cse.js?cx=015848178315289032903:hqkynptgd1o — 200 — 3.7 KiB — 107 ms — h2https://www.google.com/cse/static/element/b33cba5881f68fbf/cse_element__en.js?usqp=CAI%3Dwww.google.com/cse/static/element/b... https://www.google.com/cse/static/element/b33cba5881f68fbf/cse_element__en.js?usqp=CAI%3D — 200 — 98.5 KiB — 92 ms — h3https://www.google.com/cse/static/element/b33cba5881f68fbf/default_v6+en.csswww.google.com/cse/static/element/b... https://www.google.com/cse/static/element/b33cba5881f68fbf/default_v6+en.css — 200 — 9.7 KiB — 64 ms — h3https://www.google.com/cse/static/style/look/v6/default.csswww.google.com/cse/static/style/loo... https://www.google.com/cse/static/style/look/v6/default.css — 200 — 1.2 KiB — 54 ms — h3https://www.google.com/cse/static/element/b33cba5881f68fbf/mobile_v6+en.csswww.google.com/cse/static/element/b... https://www.google.com/cse/static/element/b33cba5881f68fbf/mobile_v6+en.css — 200 — 1.5 KiB — 23 ms — h3https://cse.google.com/adsense/search/async-ads.jscse.google.com/adsense/search/async... https://cse.google.com/adsense/search/async-ads.js — 200 — 43.6 KiB — 54 ms — h2https://www.google.com/cse/static/images/2x/en/branding.pngwww.google.com/cse/static/images/2x... https://www.google.com/cse/static/images/2x/en/branding.png — 200 — 3.3 KiB — 20 ms — h3https://clients1.google.com/generate_204clients1.google.com/generate_204 https://clients1.google.com/generate_204 — 204 — 117 B — 91 ms — h2https://ep1.adtrafficquality.google/getconfig/sodar?sv=200&tid=afs&tv=1234567890&st=env&sjk=wT4iHElXQ0OkR0MUGqKU2A==&sde=1ep1.adtrafficquality.google/getconf... https://ep1.adtrafficquality.google/getconfig/sodar?sv=200&tid=afs&tv=1234567890&st=env&sjk=wT4iHElXQ0OkR0MUGqKU2A==&sde=1 — 200 — 8.1 KiB — 81 ms — h3https://www.hse.gov.uk/cdn-cgi/rum?www.hse.gov.uk/cdn-cgi/rum? https://www.hse.gov.uk/cdn-cgi/rum? — 204 — 184 B — 21 ms — h3https://www.hse.gov.uk/favicon.icowww.hse.gov.uk/favicon.ico https://www.hse.gov.uk/favicon.ico — 200 — 337 B — 26 ms — h3https://ep2.adtrafficquality.google/sodar/sodar2.jsep2.adtrafficquality.google/sodar/s... https://ep2.adtrafficquality.google/sodar/sodar2.js — 200 — 7.9 KiB — 94 ms — h2https://ep2.adtrafficquality.google/sodar/sodar2/254/runner.htmlep2.adtrafficquality.google/sodar/s... https://ep2.adtrafficquality.google/sodar/sodar2/254/runner.html — 200 — 5.8 KiB — 69 ms — h2https://pagead2.googlesyndication.com/bg/dj12lhpBI2WR1GQ6n5lcmp69XlpHOiTAWO7c9b6NTo0.jspagead2.googlesyndication.com/bg/dj... https://pagead2.googlesyndication.com/bg/dj12lhpBI2WR1GQ6n5lcmp69XlpHOiTAWO7c9b6NTo0.js — 200 — 21.6 KiB — 100 ms — h3https://ep2.adtrafficquality.google/generate_204?L01KIgep2.adtrafficquality.google/generat... https://ep2.adtrafficquality.google/generate_204?L01KIg — 204 — 40 B — 23 ms — h2https://ep1.adtrafficquality.google/pagead/sodar?id=sodar2&v=254&t=2&li=afs_1234567890&jk=wT4iHElXQ0OkR0MUGqKU2A%3D%3D&bg=!R0SlRCbNAAY2C5OeFgs7AEcBe5WfOJMwaeIkJzIVWVvrjpyuS3wlbBGgsWo7jhjhsqrRs3Q2zE8D9kN46UH-9u2O0VXI0qQBVgdJR2pz-poTxRfsZ2yobgIAAAA7UgAAAAJoAQd-ABsrkRVJuk96eVEOQtcfc0NeH_4uzUIaBUfzyogKAOFJuAgFmyDz-L6dnNqlB1eh6DmYb1x6BRPbEPB64QBzNHfHvQj9rshGYVy1p7GFC-Uw9QNwXcuy2xEEUeGRZh4GUUXe78itwE7SlmFwn-GgvGew-YE_GNLiwztPYY1moeTo5yBUbX3Js762pSbaHm6SZ5MiRcdRzPOlM1ty97YajD8VyfYbOL-9w9K6CbhHpX4OQ_dIz-EJxXZYb9HLWcdLHMHoU_Zi7Zp0YJCdXZkCg42dvr5Z08IQj2BqS9NmTCAKwLFTWdN08LhKOHLqH-0x_kJjLsxl6Edo4O187QuVAZ2ZAgHCC17pVXdB2I9I1P7xV46evyw4HO18kxYsMonbuWBhO9Rr852HQxl0aYJbXX99V6BvSzgG9FJUjfVkSd7ufSx4HHJ238_Qyp58vHm0nyX7mqzenrKfAvtR5uJkLYFEIuhO6UEiPINdjRkU8-6AtUg_eB2JzUbxBG7o-QnpuiviSB5stTDFKgDz39Ye0aYXmTUCZUdFDKIjprP5NrIp1YswASV4wbR0pTh0Qe93yTLkjQ0dhTP8nFSin9kwupDD0EkDIdJ5b14IAiZQJgAFOEoCNg7HWIB2p5QNMJFVvLDNejs3Dv_IUSZn1N_qVE_ePsUuqpJsD48bIG-JGrK3nHimhqx6ztU-VYN-68ASvMtRU9WzjiM9peU2MTCPDbpixIztZes9ufQc1j4JFESeRYPhE2VAoBH-_T4cFI2VVTnaWICjTEiDEkY2veI81iro4da-qskX_UveWneAHxOPvXfKMAaKqdj2TIaumJRKAYyJevJEpwJW9mENpCnycLMG5gKYI_nVPUYE7IF3a9SDq2YbAoLfWGZAA-XFxUngwWgORjzPmxaG9tKWo0VzXq5tMix4Kusug-pQApMFLyq06vNHx1TOBav5yGliPWRKbWxDeV7IYtIGUNur5E52OorjnhjfA30ZJszS2FUDFcUUTXGSuiKxPnn-ZqG0kpIfoWAMeP0ep1.adtrafficquality.google/pagead/... https://ep1.adtrafficquality.google/pagead/sodar?id=sodar2&v=254&t=2&li=afs_1234567890&jk=wT4iHElXQ0OkR0MUGqKU2A%3D%3D&bg=!R0SlRCbNAAY2C5OeFgs7AEcBe5WfOJMwaeIkJzIVWVvrjpyuS3wlbBGgsWo7jhjhsqrRs3Q2zE8D9kN46UH-9u2O0VXI0qQBVgdJR2pz-poTxRfsZ2yobgIAAAA7UgAAAAJoAQd-ABsrkRVJuk96eVEOQtcfc0NeH_4uzUIaBUfzyogKAOFJuAgFmyDz-L6dnNqlB1eh6DmYb1x6BRPbEPB64QBzNHfHvQj9rshGYVy1p7GFC-Uw9QNwXcuy2xEEUeGRZh4GUUXe78itwE7SlmFwn-GgvGew-YE_GNLiwztPYY1moeTo5yBUbX3Js762pSbaHm6SZ5MiRcdRzPOlM1ty97YajD8VyfYbOL-9w9K6CbhHpX4OQ_dIz-EJxXZYb9HLWcdLHMHoU_Zi7Zp0YJCdXZkCg42dvr5Z08IQj2BqS9NmTCAKwLFTWdN08LhKOHLqH-0x_kJjLsxl6Edo4O187QuVAZ2ZAgHCC17pVXdB2I9I1P7xV46evyw4HO18kxYsMonbuWBhO9Rr852HQxl0aYJbXX99V6BvSzgG9FJUjfVkSd7ufSx4HHJ238_Qyp58vHm0nyX7mqzenrKfAvtR5uJkLYFEIuhO6UEiPINdjRkU8-6AtUg_eB2JzUbxBG7o-QnpuiviSB5stTDFKgDz39Ye0aYXmTUCZUdFDKIjprP5NrIp1YswASV4wbR0pTh0Qe93yTLkjQ0dhTP8nFSin9kwupDD0EkDIdJ5b14IAiZQJgAFOEoCNg7HWIB2p5QNMJFVvLDNejs3Dv_IUSZn1N_qVE_ePsUuqpJsD48bIG-JGrK3nHimhqx6ztU-VYN-68ASvMtRU9WzjiM9peU2MTCPDbpixIztZes9ufQc1j4JFESeRYPhE2VAoBH-_T4cFI2VVTnaWICjTEiDEkY2veI81iro4da-qskX_UveWneAHxOPvXfKMAaKqdj2TIaumJRKAYyJevJEpwJW9mENpCnycLMG5gKYI_nVPUYE7IF3a9SDq2YbAoLfWGZAA-XFxUngwWgORjzPmxaG9tKWo0VzXq5tMix4Kusug-pQApMFLyq06vNHx1TOBav5yGliPWRKbWxDeV7IYtIGUNur5E52OorjnhjfA30ZJszS2FUDFcUUTXGSuiKxPnn-ZqG0kpIfoWAMeP0 — 204 — 17 B — 47 ms — h3
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
100% of JavaScript execution is third-party
First-party Third-party 742ms · 214KB · £8/mo
www.hse.gov.uk
Other
Optional
Execution 193ms
Transfer 10 KB
Monthly Cost £2/mo
www.hse.gov.uk
Other
Optional
Execution 161ms
Transfer 79 KB
Unused 45%
Monthly Cost £2/mo
Unattributable
Other
Optional
Execution 160ms
Transfer 0 KB
Monthly Cost £2/mo
www.hse.gov.uk
Other
Optional
Execution 146ms
Transfer 122 KB
Unused 60%
Monthly Cost £2/mo
cse.google.com
Other
Optional
Execution 83ms
Transfer 4 KB
Monthly Cost £1/mo

100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.

Why this matters

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

60% of www.hse.gov.uk's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

How third-party costs are calculated

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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