Performance
· 17 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.
5.35 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
20.65 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
932 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.011
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
7.53 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.
28.21 s
Page Load Progression
FPage Weight BudgetAction6.2 MB transferred, 116 requestsFIX
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.
Source: web.dev
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
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
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.
High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.
Source: web.dev
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
FJS Execution CostAction7719ms total JS executionFIX
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.readcube.com/ | 1782ms | 100ms | 18ms | 3rd |
| Unattributable | 1037ms | 18ms | 0ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-MCT77F4P | 763ms | 673ms | 81ms | 3rd |
| https://unpkg.com/gsap@3/dist/ScrollTrigger.min.js | 661ms | 141ms | 0ms | 3rd |
| https://unpkg.co/gsap@3/dist/gsap.min.js | 636ms | 62ms | 12ms | 3rd |
| https://www.readcube.com/cdn-cgi/challenge-platform/scripts/jsd/main.js | 484ms | 454ms | 4ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-FMT5SQJ46L&cx=c>m=4e64k0 | 459ms | 366ms | 90ms | 3rd |
| https://cdn.cookielaw.org/scripttemplates/202601.2.0/otBannerSdk.js | 457ms | 274ms | 91ms | 3rd |
| https://www.readcube.com/wp-includes/js/jquery/jquery.min.js?ver=3.7.1 | 437ms | 310ms | 13ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-1009772145&cx=c>m=4e64k0 | 374ms | 242ms | 83ms | 3rd |
Showing top 10 of 16 scripts
DPage Weight InventoryAction116 resources · 6.2 MB · 196 KB savings availableFIX
~196.0 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 116 resources | 6.2 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BImage Optimization26 images, 0 KB saveableREVIEW
CJS BundlesAction36 scripts, 196 KB unusedREVIEW
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtag/js?id=G-FMT5SQJ46L&cx=c>m=4e64k0 | 173 KB | 69 KB (40%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-1009772145&cx=c>m=4e64k0 | 146 KB | 64 KB (44%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-MCT77F4P | 154 KB | 63 KB (41%) | ✓ | 3rd |
| https://www.readcube.com/wp-content/plugins/bb-plugin/js/libs/jquery.magnificpopup.min.js?ver=2.10.0.6 | 9 KB | — | ✓ | 3rd |
| https://www.readcube.com/wp-content/plugins/event-tickets/build/js/rsvp.js?ver=5.27.4 | 1 KB | — | ✓ | 3rd |
| https://unpkg.com/gsap@3.15.0/dist/gsap.min.js | 28 KB | — | ✓ | 3rd |
| https://www.readcube.com/wp-content/plugins/bb-plugin/js/libs/jquery.imagesloaded.min.js?ver=2.10.0.6 | 3 KB | — | ✓ | 3rd |
| https://www.readcube.com/wp-includes/js/masonry.min.js?ver=4.2.2 | 9 KB | — | ✓ | 3rd |
| https://www.readcube.com/wp-content/plugins/betterdocs/assets/blocks/categorygrid/frontend.js?ver=a4a7e7ed1fd9a2aaf85a | 1 KB | — | ✓ | 3rd |
| https://www.readcube.com/wp-content/plugins/the-events-calendar/common/build/js/user-agent.js?ver=da75d0bdea6dde3898df | 1 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
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
No green hosting detected
A+Text CompressionAll text resources are compressedPASS
A+Font Loading9 fonts (485 KB)PASS
Web fonts
9
485 KB total
Render-blocking
0
of 9
Dominant font-display
swap
Most common across fonts
Font loading timeline
- Convert to woff2 for ~30% smaller file size
- Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
- Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
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 ~137 KB and ~274 ms
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource Hints5 hints, 0 missing preconnectsPASS
Current Resource Hints
5 resource hints configured
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
A+Third-Party ResourcesNo third-party resources detectedPASS
Network Waterfall116 requests over 2472msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.readcube.com www.readcube.com | Other | 1782ms | 21 KB | — | €19/mo | Costly |
Unattributable Unattributable | Other | 1037ms | 0 KB | — | €11/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 763ms | 154 KB | 41% | €8/mo | Costly |
unpkg unpkg.com | CDN | 661ms | 0 KB | — | €7/mo | Costly |
unpkg.co unpkg.co | Other | 636ms | 0 KB | — | €7/mo | Costly |
www.readcube.com www.readcube.com | Other | 484ms | 0 KB | — | €5/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 459ms | 173 KB | 40% | €5/mo | Costly |
OneTrust cdn.cookielaw.org | Consent | 457ms | 128 KB | — | €5/mo | Essential |
www.readcube.com www.readcube.com | Other | 437ms | 33 KB | — | €5/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 374ms | 146 KB | 44% | €4/mo | Costly |
www.readcube.com www.readcube.com | Other | 301ms | 11 KB | — | €3/mo | Costly |
www.readcube.com www.readcube.com | Other | 93ms | 4 KB | — | €1/mo | Optional |
www.readcube.com www.readcube.com | Other | 70ms | 14 KB | — | €1/mo | Optional |
OneTrust cdn.cookielaw.org | Consent | 64ms | 3 KB | — | €1/mo | Essential |
www.readcube.com www.readcube.com | Other | 51ms | 6 KB | — | €1/mo | Optional |
OneTrust cdn.cookielaw.org | Consent | 51ms | 9 KB | — | €1/mo | Essential |
These scripts may cost more than they're worth
- www.readcube.com adds 1782ms and costs ~€19/month
- Unattributable adds 1037ms and costs ~€11/month
- Google Tag Manager adds 763ms and costs ~€8/month
- unpkg adds 661ms and costs ~€7/month
- unpkg.co adds 636ms and costs ~€7/month
- www.readcube.com adds 484ms and costs ~€5/month
- Google Tag Manager adds 459ms and costs ~€5/month
- www.readcube.com adds 437ms and costs ~€5/month
- Google Tag Manager adds 374ms and costs ~€4/month
- www.readcube.com adds 301ms and costs ~€3/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
www.readcube.com takes 1782ms 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
Unattributable takes 1037ms 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
Google Tag Manager takes 763ms 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
unpkg takes 661ms 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
unpkg.co takes 636ms 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
www.readcube.com takes 484ms 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
Google Tag Manager takes 459ms 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
www.readcube.com takes 437ms 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
Google Tag Manager takes 374ms 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
www.readcube.com takes 301ms 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