It's time for another entry in the DELIVTERMS series here on Spam Resource, where we define deliverability and email technology terms to help make them easier for email senders to understand. Today, we’re tackling a marketing term, specifically, explaining what we’re referring to when talking about an email message’s “pre-header.”
Wondering where the pre-header is, exactly? It is not an email header. Nor is it something specified in RFC 5321 or 5322; nothing there contains any definition for a second subject line or instructions for where and how to display this “pre-header” text in email clients, much less how to transmit it over SMTP.
It is, in fact, a design artifact. A bit of a design hack. It takes advantage of the fact that just about all email clients, whether they be mobile or webmail or desktop, will display a tiny teaser of the content of an email message, highlighting the first bits of text found in an email message’s body. They display this preview text in the list of emails in the inbox, usually just after the subject line.
Marketers eventually learned that they could specify specific text to display in this area by front-loading it at the top of the email message body. And while they wanted it to display as part of this preview process, they typically didn’t want that text to actually display in the body of the message. (It might reflect the message content, but the placement of this first bit of text usually isn’t optimal for the readable email copy.) To this end, marketers often use a bit of CSS design trickery when implementing this, making the pre-header text invisible when viewing the full message.
That, in a nutshell, is the pre-header. A short block of text at the top of the HTML email, positioned to display as preview information in an email client, styled to blend into or hide when viewing the full email message. The pre-header is meant to display pre-opening, before viewing, as a second subject line, a peek into some bit of message content, before opening that message.
Many email marketers love the pre-header field, finding that a well-crafted pre-header can help improve engagement rates, helping to boost the chances that a recipient will read an email message or buy the product being advertised, in the same way the perfect subject line can help.
Many email marketing platforms offer up “pre-header” as a discrete field in the interface used to compose messages and content. (Indeed, in my deliverability product management role for an email platform way back in circa 2014, I myself designed and managed implementation of pre-header functionality in a well known email marketing platform, treating it in the user interface as if it were its own header.) Which could make you think that it’s on par with a from line or subject line as far as importance to a message. It’s not implemented the same way as these very necessary email headers, but its importance to email marketers is clear.
The future, however, is less clear. Starting with iOS 18 and MacOS 15, Apple Intelligence can summarize messages for users automatically, and that quick summary is displayed where the pre-header content would have previously displayed. That means, that if you’ve got a newer Apple device, and you’ve got email summaries enabled, you’re no longer going to see pre-header content.
Over time that means less of the hand-crafted pre-header will show to Apple Mail users. But that rollout will take a while, and for now the classic hidden-text trick still shows up on plenty of iPhones and Macs, given that any Apple mobile device before the iPhone 15 isn’t able to utilize the new Apple A.I., and therefore, cannot summarize email messages on-device.
(Incidentally, Gmail’s previews work differently and don’t seem to overwrite the pre-header display, at least in my testing today. Things could change in the future, though!)
As Apple is such a big player when it comes to the mobile email client ecosystem, their gradual reclaiming of this specific real estate does suggest that the pre-header is likely to become a thing of the past. At some point. But not quite yet.
In the meantime: Marketers still use it. Inbox providers and email clients (mostly) display it. And for now, it still helps get clicks.
And if you want to learn more about email deliverability and technology, along with the occasional marketing term, too, be sure to check the DELIVTERMS section here on the Spam Resource website. There’s more to share, and more to learn!
It's time for another entry in the DELIVTERMS series here on Spam Resource, where we define deliverability and email technology terms to help make them easier for email senders to understand. Today, we’re tackling a marketing term, specifically, explaining what we’re referring to when talking about an email message’s “pre-header.”
Wondering where the pre-header is, exactly? It is not an email header. Nor is it something specified in RFC 5321 or 5322; nothing there contains any definition for a second subject line or instructions for where and how to display this “pre-header” text in email clients, much less how to transmit it over SMTP.
It is, in fact, a design artifact. A bit of a design hack. It takes advantage of the fact that just about all email clients, whether they be mobile or webmail or desktop, will display a tiny teaser of the content of an email message, highlighting the first bits of text found in an email message’s body. They display this preview text in the list of emails in the inbox, usually just after the subject line.
Marketers eventually learned that they could specify specific text to display in this area by front-loading it at the top of the email message body. And while they wanted it to display as part of this preview process, they typically didn’t want that text to actually display in the body of the message. (It might reflect the message content, but the placement of this first bit of text usually isn’t optimal for the readable email copy.) To this end, marketers often use a bit of CSS design trickery when implementing this, making the pre-header text invisible when viewing the full message.
That, in a nutshell, is the pre-header. A short block of text at the top of the HTML email, positioned to display as preview information in an email client, styled to blend into or hide when viewing the full email message. The pre-header is meant to display pre-opening, before viewing, as a second subject line, a peek into some bit of message content, before opening that message.
Many email marketers love the pre-header field, finding that a well-crafted pre-header can help improve engagement rates, helping to boost the chances that a recipient will read an email message or buy the product being advertised, in the same way the perfect subject line can help.
Many email marketing platforms offer up “pre-header” as a discrete field in the interface used to compose messages and content. (Indeed, in my deliverability product management role for an email platform way back in circa 2014, I myself designed and managed implementation of pre-header functionality in a well known email marketing platform, treating it in the user interface as if it were its own header.) Which could make you think that it’s on par with a from line or subject line as far as importance to a message. It’s not implemented the same way as these very necessary email headers, but its importance to email marketers is clear.
The future, however, is less clear. Starting with iOS 18 and MacOS 15, Apple Intelligence can summarize messages for users automatically, and that quick summary is displayed where the pre-header content would have previously displayed. That means, that if you’ve got a newer Apple device, and you’ve got email summaries enabled, you’re no longer going to see pre-header content.
Over time that means less of the hand-crafted pre-header will show to Apple Mail users. But that rollout will take a while, and for now the classic hidden-text trick still shows up on plenty of iPhones and Macs, given that any Apple mobile device before the iPhone 15 isn’t able to utilize the new Apple A.I., and therefore, cannot summarize email messages on-device.
(Incidentally, Gmail’s previews work differently and don’t seem to overwrite the pre-header display, at least in my testing today. Things could change in the future, though!)
As Apple is such a big player when it comes to the mobile email client ecosystem, their gradual reclaiming of this specific real estate does suggest that the pre-header is likely to become a thing of the past. At some point. But not quite yet.
In the meantime: Marketers still use it. Inbox providers and email clients (mostly) display it. And for now, it still helps get clicks.
And if you want to learn more about email deliverability and technology, along with the occasional marketing term, too, be sure to check the DELIVTERMS section here on the Spam Resource website. There’s more to share, and more to learn!
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