Performance
· 15 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.
581 ms
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
1.51 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
11 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.
1.46 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.
2.04 s
Page Load Progression
DPage Weight BudgetAction2.3 MB transferred, 78 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
DJS BundlesAction27 scripts, 342 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://players.brightcove.net/2310970326001/Yk2siaFBf_default/index.min.js | 326 KB | 188 KB (58%) | ✓ | 3rd |
| https://imasdk.googleapis.com/js/sdkloader/ima3_debug.js | 160 KB | 102 KB (64%) | ✓ | 3rd |
| https://cc.cdn.civiccomputing.com/9/cookieControl-9.11.min.js | 123 KB | 52 KB (42%) | ✓ | 3rd |
| https://www.metoffice.gov.uk/webfiles/1764673469274/js/common/geohash-location.js | 1 KB | — | ✓ | 3rd |
| https://www.metoffice.gov.uk/webfiles/1764673469274/js/preview-block/lazy-load-preview-block.js | 0 KB | — | ✓ | 3rd |
| https://www.metoffice.gov.uk/static/js/external/latlon-geohash/latlon-geohash@2.0.0.js | 1 KB | — | ✓ | 3rd |
| https://www.metoffice.gov.uk/webfiles/1764673469274/js/common/set-body-class.js | 1 KB | — | ✓ | 3rd |
| https://www.metoffice.gov.uk/webfiles/1764673469274/js/minified/global.min.js | 9 KB | — | ✓ | 3rd |
| https://cdnjs.cloudflare.com/ajax/libs/iamdustan-smoothscroll/0.4.0/smoothscroll.min.js | 2 KB | — | ✓ | 3rd |
| https://www.metoffice.gov.uk/webfiles/1764673469274/js/common/run-scripts-requiring-consent.js | 2 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
DPage Weight InventoryAction78 resources · 2.3 MB · 342 KB savings availableFIX
~341.9 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 78 resources | 2.3 MiB | ||||||
BImage Optimization25 images, 0 KB saveableREVIEW
Set explicit width and height to prevent CLS.
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
BJS Execution Cost608ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://players.brightcove.net/2310970326001/Yk2siaFBf_default/index.min.js | 239ms | 187ms | 27ms | 3rd |
| Unattributable | 127ms | 2ms | 0ms | 3rd |
| https://www.metoffice.gov.uk/ | 120ms | 5ms | 1ms | 3rd |
| https://www.metoffice.gov.uk/public/gdpr-consent/cookieControl-config.js?1764673469274 | 67ms | 35ms | 0ms | 3rd |
| https://cc.cdn.civiccomputing.com/9/cookieControl-9.11.min.js | 54ms | 45ms | 9ms | 3rd |
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
No green hosting detected
BHTTP Cachingmax-age=0REVIEW
max-age=0
| Directive | Value | Meaning |
|---|---|---|
| max-age | 0 | Cache for 0 seconds |
A+Text CompressionAll text resources are compressedPASS
A+Font Loading5 fonts (303 KB)PASS
Web fonts
5
303 KB total
Render-blocking
0
of 5
Dominant font-display
swap
Most common across fonts
Font loading timeline
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
- Convert to woff2 for ~30% smaller file size
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)
Fixing the unchecked items could save ~91 KB and ~182 ms
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
Network Waterfall78 requests over 1133msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
players.brightcove.net players.brightcove.net | Other | 239ms | 326 KB | 58% | £2/mo | Costly |
Unattributable Unattributable | Other | 127ms | 0 KB | — | £1/mo | Optional |
www.metoffice.gov.uk www.metoffice.gov.uk | Other | 120ms | 15 KB | — | £1/mo | Optional |
www.metoffice.gov.uk www.metoffice.gov.uk | Other | 67ms | 2 KB | — | £1/mo | Optional |
cc.cdn.civiccomputing.com cc.cdn.civiccomputing.com | Other | 54ms | 123 KB | 42% | £1/mo | Optional |
These scripts may cost more than they're worth
- players.brightcove.net adds 239ms 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
players.brightcove.net takes 239ms 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
58% of players.brightcove.net'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