Anti-Flicker Script

An anti-flicker script is a piece of JavaScript used by many Client-Side A/B Testing tools. Its purpose is to prevent the Flicker Effect, where a user briefly sees the original page before the test version loads and replaces it. The script works by hiding the entire page content until the test variation is ready to be displayed. While this solves the flicker, it introduces a significant performance penalty by forcing the user to look at a blank screen, which negatively impacts crucial metrics like Largest Contentful Paint (LCP).