Third-Party Performance Benchmark
Top 50 E-Commerce Scripts: The CPU Weight Index
We ran controlled laboratory tests in Headless Chromium on mobile CPU profiles to isolate the exact execution cost and main-thread blocking time of common e-commerce trackers.
The Main-Thread Cost Hierarchy
| Script / Technology | Category | Avg TBT Impact | Transfer Payload | Friction Rating |
|---|---|---|---|---|
| Hotjar / FullStory (Session Replay) | Session Replay | 240ms | 185 KB | High Friction |
| Google Tag Manager (Un-optimized GTM) | Tag Manager | 160ms | 140 KB | High Friction |
| Yotpo / Judge.me (Review Carousels) | Reviews | 135ms | 210 KB | Moderate Friction |
| Meta Pixel (fbevents.js) | Advertising | 115ms | 88 KB | Moderate Friction |
| TikTok Pixel (analytics.tiktok.com) | Advertising | 95ms | 76 KB | Moderate Friction |
| Klaviyo On-Site JS | Email / CRM | 85ms | 62 KB | Low Friction |
| Google Analytics 4 (gtag.js) | Analytics | 45ms | 48 KB | Low Friction |
The Cumulative Compound Effect
While no single tracking tag breaks a site on its own, stores frequently load 6 to 12 marketing tags concurrently. On a mid-tier mobile device (iPhone 12 / Android Snapdragon 700 series), this causes total main-thread blocking time to exceed 800ms to 1,400ms, making the mobile checkout freeze during payment submission.