如何使用 Next.js 與 Vercel Edge Config 打造零 CLS 的 A/B 測試
Original: How to build zero-CLS A/B tests with Next.js and Vercel Edge Config
In modern web development, A/B testing is an indispensable tool for optimizing conversion rates. However, traditional client-side…
傳統客戶端 A/B 測試常因延遲載入實驗版本而導致網頁佈局偏移（CLS），影響使用者體驗與 SEO。本文介紹如何利用 Next.js Middleware 與 Vercel Edge Config 的超低延遲讀取特性，在 Edge 邊緣端即時決定用戶分流並進行重寫（Rewrite）。這種做法能讓瀏覽器直接接收到最終渲染的 HTML，實現完全無閃爍、零 CLS 的高效能 A/B 測試。
In modern web development, A/B testing is an indispensable tool for optimizing conversion rates. However, traditional client-side JavaScript-based A/B testing solutions — such as those from Google Optimize or Optimizely — typically swap out components dynamically after the page has already loaded in the browser. This causes severe Cumulative Layout Shift (CLS), which damages Core Web Vitals scores and lowers SEO rankings.
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