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https://www.britishairways.com

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
77
GRADE
C
FIX
4
REVIEW
2
PASS
6
INFO
2

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

Mobile Desktop
55
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
89
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
92
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
92
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.

785 ms

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

3.47 s

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

274 ms

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

0.140

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

5.45 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.

3.59 s

Page Load Progression

1.0 s
2.1 s
3.1 s
4.1 s
5.1 s
6.2 s
7.2 s
8.2 s
Checks
14
6 PASS 2 REVIEW 4 FIX
F
Page Weight Budget
Action
3.6 MB transferred, 149 requests
FIX
3.6 MB transferred, 149 requests
Warning::
Page weighs 8.8 MB (3.6 MB transferred)
Warning::
JavaScript is 2.2 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 2.2 MB
Info::
Fonts are 443 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 443 KB
Info::
CSS is 255 KB — consider purging unused styles
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
Got: 255 KB
Warning::
149 HTTP requests — consider bundling or reducing
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
Info::
Estimated 0.75 g CO2 per page load
3.6 MB / 2.4 MB budget
3.6 MB transferred
149 requests
0.75 g CO2 per page load
JavaScript 2.2 MiB 61%
Images 573.5 KiB 16%
Fonts 443.0 KiB 12%
CSS 254.9 KiB 7%
Other 69.9 KiB 2%
HTML 40.7 KiB 1%
Other 12.7 KiB 0%
Other 11.4 KiB 0%
Other 5.4 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

Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.

Why this matters

CSS bundle is large — purge unused styles (PurgeCSS, Tailwind JIT) to reduce CSS payload.

Source: web.dev

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
JS Execution Cost
Action
2121ms total JS execution
FIX
2121ms total JS execution
Warning::
https://www.britishairways.com/nx/b/homepage/_next...: 539ms CPU time
Warning::
Unattributable: 328ms CPU time
Warning::
https://tagman.britishairways.com/britishairways/n...: 294ms CPU time
Warning::
https://www.britishairways.com/nx/b/homepage/_next...: 256ms CPU time
Warning::
https://www.britishairways.com/JgkOWn/cQeAhL/WYaC/...: 252ms CPU time
Info::
Third-party scripts: 622ms (29% of total)

Main Thread Breakdown

Script Evaluation 63% Other 18% Script Parsing & Compilation 8% Style & Layout 5%
ScriptTotalScriptingParse/CompileParty
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/framework-3d9cad9dc1d09675.js539ms447ms6ms1st
Unattributable328ms62ms0ms3rd
https://tagman.britishairways.com/britishairways/nexus-prod/Bootstrap.js294ms225ms14ms3rd
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/pages/_app-8e5554fa8766420d.js256ms166ms72ms1st
https://www.britishairways.com/JgkOWn/cQeAhL/WYaC/o28gIw/wW/LYX52JSEaObEL0uEii/VzsYMAE/ZzsgHE/YRISwB252ms214ms16ms1st
https://www.britishairways.com/travel/home/public/fr_fr/177ms14ms5ms1st
https://www.britishairways.com/JgkOWn/cQeAhL/WYaC/o28gIw/wW/tbX52JSEaObE/GkghMAE/bD5LE0/I9e2dt?v=1efa545a-638a-6437-5ec1-8bb035b75435166ms147ms15ms1st
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/pages/index-27990ef2704a9dca.js55ms54ms0ms1st
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/748-587cd0e2d888bbd0.js54ms8ms21ms1st
F
JS Bundles
Action
19 scripts, 809 KB unused
FIX
19 scripts, 809 KB unused
Warning::
https://www.britishairways.com/nx/b/homepage/_next...: 481 KB unused (54%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.britishairways.com/nx/b/homepage/_next...: 75 KB unused (35%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://tagman.britishairways.com/britishairways/n...: 58 KB unused (49%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.britishairways.com/nx/b/homepage/_next...: 52 KB unused (68%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://s.go-mpulse.net/boomerang/93U6S-JS5E3-HQLJ...: 41 KB unused (73%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 809 KB
809 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/pages/_app-8e5554fa8766420d.js906 KB481 KB (54%)✓1st
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/748-587cd0e2d888bbd0.js242 KB75 KB (35%)✓1st
https://tagman.britishairways.com/britishairways/nexus-prod/Bootstrap.js119 KB58 KB (49%)✓3rd
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/294-19da17d576ea4783.js81 KB52 KB (68%)✓1st
https://s.go-mpulse.net/boomerang/93U6S-JS5E3-HQLJ8-98G8C-NNRXF56 KB41 KB (73%)✓3rd
https://www.britishairways.com/JgkOWn/cQeAhL/WYaC/o28gIw/wW/LYX52JSEaObEL0uEii/VzsYMAE/ZzsgHE/YRISwB180 KB38 KB (21%)✓1st
https://www.britishairways.com/JgkOWn/cQeAhL/WYaC/o28gIw/wW/tbX52JSEaObE/GkghMAE/bD5LE0/I9e2dt?v=1efa545a-638a-6437-5ec1-8bb035b75435162 KB34 KB (21%)✓1st
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/framework-3d9cad9dc1d09675.js69 KB30 KB (47%)✓1st
https://www.britishairways.com/nx/b/homepage/_next/static/chunks/5ce8f35c-498c238a70038099.js345 KB—✓1st
https://www.britishairways.com/nx/b/homepage/_next/static/Po9JbVd0utDhbDkc6VCED/_ssgManifest.js5 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

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

D
HTTP Caching
Action
no-store (uncacheable)
FIX
no-store (uncacheable)
Info::
Cache-Control: no-store prevents all caching
Intentional for dynamic content, but increases server load for every page view.
Got: no-cache, no-store, must-revalidate
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

no-cache, no-store, must-revalidate

DirectiveValueMeaning
no-cache—Cache but always revalidate first
no-store—Never cache this response
must-revalidate—Must recheck with server after expiry
B
Image Optimization
36 images, 0 KB saveable
REVIEW
36 images, 0 KB saveable
Warning::
https://www.britishairways.com/nx/b/static/logos/s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
36 images 534 KB
0 oversized -0 KB
13 legacy format
1 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

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

Green Hosting

No green hosting detected

A
Third-Party Impact
26% third-party, 0 ms blocking
PASS
26% third-party, 0 ms blocking
Info::
Third-party code accounts for 26% of page weight (943.5 KiB of 3.6 MiB)
Info::
Third-party blocking time is low (0 ms)
74%
26%
First-party Third-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+
Font Loading
7 fonts (443 KB)
PASS
7 fonts (443 KB)
Info::
7 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

7

443 KB total

Render-blocking

0

of 7

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 1.0 s 2.0 s 3.0 s FCP 785 ms LCP 3.5 shttps://www.britishairways.com/nx/b/static/fonts/mylius-modern-reg.ttfmylius-modern-reg.ttf https://www.britishairways.com/nx/b/static/fonts/mylius-modern-reg.ttf — 60.4 KiB — 0 ms — font-display: swaphttps://www.britishairways.com/nx/b/static/fonts/mylius-modern-lt.ttfmylius-modern-lt.ttf https://www.britishairways.com/nx/b/static/fonts/mylius-modern-lt.ttf — 60.2 KiB — 0 ms — font-display: swapdata:font/ttf;base64,AAEAAAARAQAABAAQR0RFRgAQAN0AAGs4AAAAFkdQT1MAGQAMAABrUAAAABBHU1VC3c7emwAAa2AAAA…ttf;base64,AAEAAAARAQAA... data:font/ttf;base64,AAEAAAARAQAABAAQR0RFRgAQAN0AAGs4AAAAFkdQT1MAGQAMAABrUAAAABBHU1VC3c7emwAAa2AAAA… — 27.0 KiB — 0 ms — font-display: swapdata:font/ttf;base64,AAEAAAASAQAABAAgRkZUTVrkl94AAYDMAAAAHEdERUYAJwH3AAFNEAAAAB5HUE9Tbe9IegABTYAAAD…ttf;base64,AAEAAAASAQAA... data:font/ttf;base64,AAEAAAASAQAABAAgRkZUTVrkl94AAYDMAAAAHEdERUYAJwH3AAFNEAAAAB5HUE9Tbe9IegABTYAAAD… — 96.2 KiB — 0 ms — font-display: swapdata:font/ttf;base64,AAEAAAASAQAABAAgRkZUTVrkmw8AAX24AAAAHEdERUYAJwH4AAFIpAAAAB5HUE9T1wrbsAABSRQAAD…ttf;base64,AAEAAAASAQAA... data:font/ttf;base64,AAEAAAASAQAABAAgRkZUTVrkmw8AAX24AAAAHEdERUYAJwH4AAFIpAAAAB5HUE9T1wrbsAABSRQAAD… — 95.5 KiB — 0 ms — font-display: swapdata:font/ttf;base64,AAEAAAARAQAABAAQR0RFRgAQAN0AAGbcAAAAFkdQT1MAGQAMAABm9AAAABBHU1VC3c7emwAAZwQAAA…ttf;base64,AAEAAAARAQAA... data:font/ttf;base64,AAEAAAARAQAABAAQR0RFRgAQAN0AAGbcAAAAFkdQT1MAGQAMAABm9AAAABBHU1VC3c7emwAAZwQAAA… — 25.9 KiB — 0 ms — font-display: swaphttps://www.britishairways.com/nx/b/static/fonts/mylius-modern-bd.ttfmylius-modern-bd.ttf https://www.britishairways.com/nx/b/static/fonts/mylius-modern-bd.ttf — 77.9 KiB — 0 ms — font-display: swap
mylius-modern-reg.ttf ttf swap
Size 60 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
mylius-modern-lt.ttf ttf swap
Size 60 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
ttf;base64,AAEAAAARAQAA... unknown swap
Size 27 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
ttf;base64,AAEAAAASAQAA... unknown swap
Size 96 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
ttf;base64,AAEAAAASAQAA... unknown swap
Size 95 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
ttf;base64,AAEAAAARAQAA... unknown swap
Size 26 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
mylius-modern-bd.ttf ttf swap
Size 78 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • 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 ~133 KB and ~266 ms

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
Network Waterfall
149 requests over 0ms
INFO

Performance analysis not available for this result.

Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
29% of JavaScript execution is third-party
First-party Third-party 622ms · 119KB · £6/mo
Unattributable
Other
Costly
Execution 328ms
Transfer 0 KB
Monthly Cost £3/mo
tagman.britishairways.com
Other
Costly
Execution 294ms
Transfer 119 KB
Unused 49%
Monthly Cost £3/mo

These scripts may cost more than they're worth

  • Unattributable adds 328ms and costs ~£3/month
  • tagman.britishairways.com adds 294ms and costs ~£3/month

Unattributable takes 328ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

tagman.britishairways.com takes 294ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

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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