A/B testing (split testing) sends variant A and variant B to a sample of your list, then sends the winning variant to the remainder. Most commonly tested: subject lines, send times, and CTA copy. Even small improvements compound — a 5% open rate lift on a 10,000-subscriber list means 500 more opens per send. InfluencersKit includes A/B testing on Creator plans; many competitor platforms gate it to higher tiers.