The email preheader is the short snippet of text that appears next to an email’s subject line in a user’s inbox. The preheader is intended to provide a brief preview or summary of the email content to give the recipient more context before opening the message. For email marketers, preheaders provide a valuable opportunity to enhance an email's subject line and entice recipients to open the message.
Although writing a preheader is not required to send an email, doing so is considered best practice for commercial email and typically increases email open and engagement rates.
Explore the OneSignal Email Performance Guide to check out some examples of good preheaders, poor preheaders, and more email optimizations for higher-performing emails.