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.
746 ms
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
1.76 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
53 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.
1.18 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.
2.22 s
Page Load Progression
DThird-Party ImpactAction100% third-party, 0 ms blockingFIX
FJS BundlesAction7 scripts, 312 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtag/js?id=G-XT3P0H8SMY&l=dataLayerForGoogleTagManager&cx=c>m=4e64h1 | 180 KB | 70 KB (39%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-T8CXXNC&l=dataLayerForGoogleTagManager | 161 KB | 69 KB (43%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-928025474&l=dataLayerForGoogleTagManager&cx=c>m=4e64h1 | 147 KB | 66 KB (45%) | ✓ | 3rd |
| https://player.flipsnack.com/reader-bridge.gz.js | 187 KB | 40 KB (62%) | ✗ | 3rd |
| https://cdn.flipsnack.com/site/dist/genericv2.dbd387c09f8de4b79849.js | 52 KB | 34 KB (67%) | ✓ | 3rd |
| https://cdn.flipsnack.com/site/dist/site-base.44ae0c81dcd683c648a9.js | 51 KB | 32 KB (63%) | ✓ | 3rd |
| https://cdn.flipsnack.com/site/accessibility.min.js | 30 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
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
DPage Weight InventoryAction76 resources · 1.3 MB · 312 KB savings availableFIX
~311.9 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 76 resources | 1.3 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BPage Weight Budget1.3 MB transferred, 76 requestsREVIEW
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
BImage Optimization53 images, 0 KB saveableREVIEW
CJS Execution CostAction1280ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.flipsnack.com/ | 378ms | 11ms | 1ms | 3rd |
| Unattributable | 262ms | 6ms | 0ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-XT3P0H8SMY&l=dataLayerForGoogleTagManager&cx=c>m=4e64h1 | 197ms | 169ms | 25ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-T8CXXNC&l=dataLayerForGoogleTagManager | 99ms | 77ms | 21ms | 3rd |
| https://cdn.flipsnack.com/site/dist/site-base.44ae0c81dcd683c648a9.js | 87ms | 58ms | 8ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-928025474&l=dataLayerForGoogleTagManager&cx=c>m=4e64h1 | 84ms | 64ms | 19ms | 3rd |
| https://cdn.flipsnack.com/site/accessibility.min.js | 65ms | 41ms | 5ms | 3rd |
| https://player.flipsnack.com/reader-bridge.gz.js | 54ms | 17ms | 36ms | 3rd |
| https://cdn.flipsnack.com/site/dist/genericv2.dbd387c09f8de4b79849.js | 53ms | 32ms | 8ms | 3rd |
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 Loading7 fonts (115 KB)PASS
Web fonts
7
115 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
Network Waterfall76 requests over 2724msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.flipsnack.com www.flipsnack.com | Other | 378ms | 26 KB | — | $5/mo | Costly |
Unattributable Unattributable | Other | 262ms | 0 KB | — | $3/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 197ms | 180 KB | 39% | $3/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 99ms | 161 KB | 43% | $1/mo | Optional |
cdn.flipsnack.com cdn.flipsnack.com | Other | 87ms | 51 KB | 63% | $1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 84ms | 147 KB | 45% | $1/mo | Optional |
cdn.flipsnack.com cdn.flipsnack.com | Other | 65ms | 30 KB | — | $1/mo | Optional |
player.flipsnack.com player.flipsnack.com | Other | 54ms | 187 KB | 62% | $1/mo | Optional |
cdn.flipsnack.com cdn.flipsnack.com | Other | 53ms | 52 KB | 67% | $1/mo | Optional |
These scripts may cost more than they're worth
- www.flipsnack.com adds 378ms and costs ~$5/month
- Unattributable adds 262ms 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.flipsnack.com takes 378ms 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 262ms 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
63% of cdn.flipsnack.com's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
62% of player.flipsnack.com's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
67% of cdn.flipsnack.com's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev