Performance
· 26 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.
3.21 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
3.48 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
304 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.
3.21 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.
3.85 s
Page Load Progression
FJS BundlesAction6 scripts, 612 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://transport.bluei.io/assets/index-QF_35YD0.js | 382 KB | 306 KB (80%) | ✓ | 1st |
| https://transport.bluei.io/assets/index-QF_35YD0.js | 0 KB | 306 KB (80%) | ✓ | 1st |
| https://transport.bluei.io/registerSW.js | 0 KB | — | ✓ | 1st |
| https://transport.bluei.io/cdn-cgi/challenge-platform/h/g/scripts/jsd/fe6331af5207/main.js? | 11 KB | — | ✓ | 1st |
| https://transport.bluei.io/registerSW.js | 0 KB | — | ✓ | 1st |
| https://transport.bluei.io/cdn-cgi/challenge-platform/h/g/scripts/jsd/fe6331af5207/main.js? | 0 KB | — | ✓ | 1st |
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
CJS Execution CostAction1919ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| Unattributable | 698ms | 1ms | 0ms | 3rd |
| https://transport.bluei.io/cdn-cgi/challenge-platform/scripts/jsd/main.js | 475ms | 438ms | 7ms | 1st |
| https://transport.bluei.io/assets/index-QF_35YD0.js | 358ms | 170ms | 169ms | 1st |
| https://transport.bluei.io/login | 237ms | 147ms | 2ms | 1st |
| https://transport.bluei.io/ | 151ms | 144ms | 1ms | 1st |
CCompression AlgorithmActionMain response served uncompressedREVIEW
BServer-Timing ObservabilityNo Server-Timing header foundREVIEW
BHTTP Cachingpublic, max-age=0REVIEW
public, max-age=0
| Directive | Value | Meaning |
|---|---|---|
| public | — | Any cache may store this response |
| max-age | 0 | Cache for 0 seconds |
A+Page Weight Budget448 KB transferred, 28 requestsPASS
A+Third-Party ImpactNo third-party resourcesPASS
A+Text CompressionAll text resources are compressedPASS
A+Image Optimization2 images, 0 KB saveablePASS
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
A+Font Loading3 fonts (29 KB)PASS
Web fonts
3
29 KB total
Render-blocking
0
of 3
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
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 ~9 KB and ~18 ms
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
A+HTTP/3 (QUIC)HTTP/3 advertised via Alt-SvcPASS
A+LCP Image PreloadLCP preload audit not availablePASS
A+Main HTML Cache-ControlMain HTML max-age=0 (≤ 5min) is appropriatePASS
A+Server Response Intelligence2 server-response signal(s) detectedPASS
APage Weight Inventory28 resources · 448 KB · 612 KB savings availablePASS
~611.9 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 28 resources | 447.8 KiB | ||||||
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
A+Third-Party ResourcesNo third-party resources detectedPASS
AJavaScript Blocking1 JS blocking issue(s) detectedPASS
A+CSS Performance DepthNo CSS performance depth issues detectedPASS
A+Green HostingWhether the site is served from green-energy infrastructurePASS
Green Hosting
This site is hosted on green energy infrastructure
Provider: Cloudflare
Network Waterfall28 requests over 865msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
Unattributable Unattributable | Other | 698ms | 0 KB | — | £7/mo | Costly |
These scripts may cost more than they're worth
- Unattributable adds 698ms and costs ~£7/month
Unattributable takes 698ms 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
Image Optimization1 images, 25 KB total, 25 KB wastedINFO
Image Optimization Audit
Total Images
1
Total Size
25 KB
Oversized
1
Wasted
25 KB