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Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
80
GRADE
B
FIX
3
REVIEW
3
PASS
8
INFO
1

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

Mobile Desktop
6
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
86
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.

6.67 s

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

13.44 s

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

2.96 s

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

0.801

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

6.67 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.

22.43 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
15
8 PASS 3 REVIEW 3 FIX
F
Page Weight Budget
Action
3.4 MB transferred, 154 requests
FIX
3.4 MB transferred, 154 requests
Warning::
Page weighs 9.1 MB (3.4 MB transferred)
Warning::
JavaScript is 1.7 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.7 MB
Info::
Fonts are 518 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 518 KB
Warning::
154 HTTP requests — consider bundling or reducing
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Info::
Estimated 0.72 g CO2 per page load
3.4 MB / 2.4 MB budget
3.4 MB transferred
154 requests
0.72 g CO2 per page load
JavaScript 1.7 MiB 51%
Images 934.5 KiB 27%
Fonts 517.8 KiB 15%
HTML 165.7 KiB 5%
Other 62.8 KiB 2%
Other 21.9 KiB 1%
Other 9.8 KiB 0%
CSS 8.6 KiB 0%
Other 2.5 KiB 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

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

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Why this matters

High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.

Source: web.dev

D
Third-Party Impact
Action
98% third-party, 0 ms blocking
FIX
98% third-party, 0 ms blocking
Warning::
Third-party code accounts for 98% of page weight (3.3 MiB of 3.4 MiB)
Info::
Third-party blocking time is low (0 ms)
98%
First-party Third-party
F
JS Bundles
Action
90 scripts, 690 KB unused
FIX
90 scripts, 690 KB unused
Warning::
https://static.files.bbci.co.uk/core/bundle-compon...: 201 KB unused (50%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://static.files.bbci.co.uk/core/bundle-produc...: 173 KB unused (77%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://static.files.bbci.co.uk/core/bundle-compon...: 80 KB unused (49%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://static.files.bbci.co.uk/core/bundle-compon...: 74 KB unused (54%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://static.files.bbci.co.uk/core/bundle-pwa.90...: 57 KB unused (90%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 690 KB
690 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://static.files.bbci.co.uk/core/bundle-component-tabs.58a9622d709c78b1f52d.js5 KB201 KB (50%)✓3rd
https://static.files.bbci.co.uk/core/bundle-product-navigation.f477a218b62f9ed3ad34.js2 KB173 KB (77%)✓3rd
https://static.files.bbci.co.uk/core/bundle-component-rich-text.ded60a5a321c891c93b7.js3 KB80 KB (49%)✓3rd
https://static.files.bbci.co.uk/core/bundle-component-portrait-video-modal.2cdc2909097fd9800d75.js5 KB74 KB (54%)✓3rd
https://static.files.bbci.co.uk/core/bundle-pwa.90632e97690d8337170a.js10 KB57 KB (90%)✓3rd
https://static.files.bbci.co.uk/core/bundle-component-image.b932d7ef5f215dc3f07c.js3 KB50 KB (73%)✓3rd
https://static.files.bbci.co.uk/core/bundle-framework.fa8250dbab749ab46b0a.js47 KB31 KB (41%)✓3rd
https://static.files.bbci.co.uk/core/bundle-portrait-video-experience.d545d11237dca3a928d2.js7 KB25 KB (45%)✓3rd
https://static.files.bbci.co.uk/core/bundle-component-promo.2eef2925e862b0780cae.js6 KB—✗3rd
https://static.files.bbci.co.uk/core/website/assets/static/scripts/riddle/riddle.b586b30e8b60901def3b.js7 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

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

B
Image Optimization
32 images, 0 KB saveable
REVIEW
32 images, 0 KB saveable
Info::
All images are well-optimized
32 images 935 KB
0 oversized -0 KB
6 legacy format
0 missing dimensions CLS risk
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

B
HTTP Caching
private, stale-if-error=90, stale-while-revalidate=30, max-age=0, must-revalidate
REVIEW
private, stale-if-error=90, stale-while-revalidate=30, max-age=0, must-revalidate
Info::
Cache-Control header is set
Got: private, stale-if-error=90, stale-while-revalidate=30, max-age=0, must-revalidate
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

private, stale-if-error=90, stale-while-revalidate=30, max-age=0, must-revalidate

DirectiveValueMeaning
private—Only browser cache, not CDN/proxy
stale-if-error90
stale-while-revalidate30Serve stale for 30 seconds while fetching fresh
max-age0Cache for 0 seconds
must-revalidate—Must recheck with server after expiry
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
No JS execution data
PASS
No JS execution data
Info::
No significant JS execution detected
A+
Font Loading
8 fonts (518 KB)
PASS
8 fonts (518 KB)
Info::
8 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

8

518 KB total

Render-blocking

0

of 8

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 12.0 s 14.0 s FCP 6.7 s LCP 13.4 shttps://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Bd.woff2BBCReithSans_W_Bd.woff2 https://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Bd.woff2 — 59.0 KiB — 0 ms — font-display: swaphttps://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Rg.woff2BBCReithSans_W_Rg.woff2 https://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Rg.woff2 — 65.6 KiB — 0 ms — font-display: swaphttps://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Md.woff2BBCReithSans_W_Md.woff2 https://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Md.woff2 — 64.5 KiB — 0 ms — font-display: swaphttps://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Rg.woff2BBCReithSans_W_Rg.woff2 https://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Rg.woff2 — 65.6 KiB — 0 ms — font-display: swaphttps://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Bd.woff2BBCReithSans_W_Bd.woff2 https://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_Bd.woff2 — 59.0 KiB — 0 ms — font-display: swaphttps://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSerif_W_Md.woff2BBCReithSerif_W_Md.woff2 https://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSerif_W_Md.woff2 — 78.0 KiB — 0 ms — font-display: swaphttps://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSerif_W_Rg.woff2BBCReithSerif_W_Rg.woff2 https://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSerif_W_Rg.woff2 — 78.7 KiB — 0 ms — font-display: swaphttps://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_ExBd.woff2BBCReithSans_W_ExBd.woff2 https://static.files.bbci.co.uk/fonts/reith/2.512/BBCReithSans_W_ExBd.woff2 — 47.4 KiB — 0 ms — font-display: swap
BBCReithSans_W_Bd.woff2 woff2 swap
Size 59 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
BBCReithSans_W_Rg.woff2 woff2 swap
Size 66 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
BBCReithSans_W_Md.woff2 woff2 swap
Size 64 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
BBCReithSans_W_Rg.woff2 woff2 swap
Size 66 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
BBCReithSans_W_Bd.woff2 woff2 swap
Size 59 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
BBCReithSerif_W_Md.woff2 woff2 swap
Size 78 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
BBCReithSerif_W_Rg.woff2 woff2 swap
Size 79 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
BBCReithSans_W_ExBd.woff2 woff2 swap
Size 47 KB
Load time 0 ms
Start 0 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+
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
154 requests over 0ms
INFO

Performance analysis not available for this result.

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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