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.
634 ms
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
2.61 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
67 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.001
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
1.35 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.
4.88 s
Page Load Progression
387 ms
775 ms
1.2 s
1.5 s 1.9 s 2.3 s 2.7 s
3.1 sFPage Weight BudgetAction7.8 MB transferred, 213 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
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 ImpactAction83% third-party, 0 ms blockingFIX
FJS BundlesAction56 scripts, 613 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604160201/pubads_impl.js | 188 KB | 142 KB (76%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-52VMX98 | 158 KB | 103 KB (65%) | ✓ | 3rd |
| https://bookshop.org/gtgbkshp/?id=G-PBC1NBK83Q&cx=c>m=4e64h1 | 172 KB | 71 KB (41%) | ✓ | 1st |
| https://bookshop.org/gtgbkshp/?id=AW-669349773&cx=c>m=4e64h1 | 150 KB | 71 KB (48%) | ✓ | 1st |
| https://bookshop.org/gtgbkshp/ | 166 KB | 67 KB (41%) | ✓ | 1st |
| https://bookshop.org/_next/static/chunks/9070-5dd99bc2aa85a519.js | 80 KB | 58 KB (72%) | ✓ | 1st |
| https://static.fbot.me/friendbuy.js | 100 KB | 46 KB (46%) | ✓ | 3rd |
| https://bookshop.org/_next/static/chunks/8193-f645ef97c581c990.js | 65 KB | 34 KB (55%) | ✓ | 1st |
| https://cmp.osano.com/mbso9YM8zJ/5bf7eaf8-0636-48dc-b8de-072565a02b02/osano.js | 70 KB | 21 KB (31%) | ✓ | 3rd |
| https://bookshop.org/_next/static/chunks/141-952efa2baa98b616.js | 13 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
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
FPage Weight InventoryAction213 resources · 7.8 MB · 613 KB savings availableFIX
~612.9 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 213 resources | 7.8 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BImage Optimization126 images, 0 KB saveableREVIEW
CJS Execution CostAction1255ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| Unattributable | 375ms | 4ms | 0ms | 3rd |
| https://bookshop.org/ | 272ms | 37ms | 16ms | 1st |
| https://bookshop.org/_next/static/chunks/2117-a7c96d3f711e8b10.js | 226ms | 209ms | 2ms | 1st |
| https://cmp.osano.com/mbso9YM8zJ/5bf7eaf8-0636-48dc-b8de-072565a02b02/osano.js | 208ms | 168ms | 12ms | 3rd |
| https://bookshop.org/gtgbkshp/ | 119ms | 100ms | 10ms | 1st |
| https://bookshop.org/gtgbkshp/?id=G-PBC1NBK83Q&cx=c>m=4e64h1 | 55ms | 46ms | 9ms | 1st |
A+Text CompressionAll text resources are compressedPASS
A+Font Loading7 fonts (290 KB)PASS
Web fonts
7
290 KB total
Render-blocking
0
of 7
Dominant font-display
swap
Most common across fonts
Font loading timeline
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 CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
A+Green HostingWhether the site is served from green-energy infrastructurePASS
Green Hosting
This site is hosted on green energy infrastructure
Provider: Cloudflare
Network Waterfall213 requests over 3061msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
Unattributable Unattributable | Other | 375ms | 0 KB | — | $5/mo | Costly |
cmp.osano.com cmp.osano.com | Other | 208ms | 70 KB | 31% | $3/mo | Costly |
These scripts may cost more than they're worth
- Unattributable adds 375ms and costs ~$5/month
- cmp.osano.com adds 208ms and costs ~$3/month
46% of JavaScript execution time comes from third-party scripts.
Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.
Learn more ▾ ▴
Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.
Source: web.dev / HTTP Archive Web Almanac
Unattributable takes 375ms 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
cmp.osano.com takes 208ms 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