While most teams I talk to would love to be able to run A/B tests to accurately assess the performance impact of certain changes, the problem is pretty much every popular A/B testing tool on the market has such a negative impact on load performance that they’re essentially unusable for this purpose.
If you’re just trying to determine which of two marketing headlines converts better, then perhaps this performance difference isn’t so bad. But if you’re wanting to run an A/B test to determine whether inlining your CSS in the
<head>of your pages will improve your FCP, well, those popular A/B testing tools are just not going to cut it.
He goes on to describe his process for running performant A/B tests on his static site using Cloudflare workers to swap in/out his experiments.