What elements can be A/B tested? (Subject lines, CTAs, content, send time)

Nearly every element of an email campaign can be A/B tested:

Subject lines testing length, tone, personalization, urgency, or emojis. Preheader text testing what appears after the subject. Sender name testing personal names versus brand names.

Email body including copy length, tone, offers, and messaging hierarchy. Images testing product shots, lifestyle imagery, or no images. CTAs testing button text, color, size, placement, and quantity.

Layout and design testing single column versus multi-column, image placement, and whitespace. Personalization testing dynamic content versus static versions.

Timing testing send day, time of day, and frequency.

Start with high-impact, easy-to-measure elements like subject lines and CTAs. These typically show the clearest results with the smallest required sample sizes.