Increase Open Rates and Engagement by Using and Testing Preheaders – Cheetah Digital Help Center

This guide describes the best practices for using preheaders, and shows how to use and test preheaders along with your subject line to increase engagement.

What is the Email Preview?

The email preview will always be the first text in the email. In an HTML email, the first text is relevant to the opened email, usually not the subject line.

What is an Email Preheader?

An email preheader is invisible text that is added to the top of an email’s HTML to become the preview, instead of the first email text. It does not appear in the actual email when it is opened.

Why Use a Preheader?

Often with HTML emails, the first text in the email is not the optimal inbox preview text for creating the response of opening the email. The first text in your email may be a link to view the email in a browser, or an unsubscribe option, for example.

The preheader allows marketers to control what the recipient will see in their inbox client - building on the subject line using the preview text below it, for the purpose of increased interest and subsequent opens and clicks.

A preheader typically elaborates on the subject line or includes a Call-To-Action.

Use the preheader to:

Entice the reader to click through
Give users an incentive
Increase open rates
Increase conversion rates
Increase website views (if you’ve included CTAs that lead to your site)

What Should the Preheader Not Be Used For?

It is not advisable to use your preheader to:

Repeat your subject line
Add your unsubscribe link
Post long preheader text, as it may be cut off.

Always place the most valuable message near the beginning of the preheader.

How Do I Add a Preheader?

Simply enter the text for your preheader. Like the subject line, it supports personalization and special characters. A counter will tell you how many characters long your preheader is.

Please note that the preheader is inserted immediately after the <body> tag in the email during merge. If there is no body tag in the actual message before merge, or the body tag is conditional, the preheader will not be added.

Personalizing the Preheader

As with the subject line, you can easily personalize the preheader by selecting a field from the personalization library and adding it. You can also paste in special characters. The counter of number of characters on the right does not include the personalization.

How Long Should the Preheader Be?

A best practice is to have the preheader not be very long.

Make it short, impactful, and easy to read
We recommend between 30 and 80 characters
Place the most important message always within the first 30 characters
Preheaders in Cheetah Messaging are automatically followed by padding that prevents the first email content from following the preheader in the preview, so you can use short preheaders that visually stand out in the crowded inbox

What is Preheader Padding?

Shorter preheaders can have a bigger impact, but without padding will be immediately followed in the preview by the first visible text from the email.

Preheader padding empties the space after the preheader, making your message more visible and easier to scan.

Cheetah Messaging automatically adds “Smart Padding” to the end of your preheader - the lengths of both subject line and preheader are considered to apply exactly the amount of padding that is needed for the two styles of inbox previews shown below, and no more.

The Number of Characters Visible in Various Types of Inbox Previews

The Gmail client in the Chrome browser, 1920x1080 resolution, set at 100% Zoom, on Windows

The subject line and preheader appear on 1 line, sharing a combined space for 194 characters.
- A long subject line means less room for the preheader

The Mail app on an iPhone 12 Max, regular text size

By default, the preheader is on 2 lines, with space for approximately 111 characters
- The more lines of preheader per message, the more a short, one-line preheader (or an empty preview, subject line only) will stand out from the wall of text

The Gmail app on an iPhone 12 Max, regular text size

The subject line and preheader appear on 2 lines, with space to show approximately 44 characters of the preheader
- Keep the valuable information and CTA in the first 30 characters as anything after 44 characters will not be seen - shorter preheaders are better

How Do I Make a “Lonely Subject Line?”

Many marketers today are using padding to have no preheader or inbox preview at all, just a lone subject line surrounded by empty white space. When the inbox is a wall of text, a subject line by itself attracts the eye. You can accomplish this easily by adding a space HTML entity (use only 1) in the preheader field. Padding will be inserted and keep the preview empty.

You can use   or ͏ or &zwnj;
Regular space characters will be ignored
Use only one HTML entity so that Smart Padding will be able to count more accurately how many spaces are needed

This shows how to create a “Lonely Subject Line:”

See the result here:

How Do I Preview the Preheaders?

Simply click on Preview to view and determine if the message and CTA created by the subject Line and preheader are appearing and working together as intended. The preheader will appear after the subject line and a hyphen, just as it will appear in the Gmail browser inbox.

The proof as it then appeared in Gmail:

Turn Off Automatic Padding If…

…padding is already part of your HTML template. This will prevent your message from becoming unnecessarily large. Check “Do Not Pad.”

Cheetah Messaging padding is “Smart,” it considers both subject line length and preheader length to adjust itself to be exactly the amount needed per message for both single-line and multiple-line style inbox previews.

If there is no preheader entered, no padding will be added. The “Do Not Pad” checkbox will not appear.
If the preheader is long enough to fill the preview, no padding will be added.
If you have your own preferred combination of HTML entities and you paste several of them after the preheader text into the preheader field, they will be counted as 6 text characters each, and no padding will be added.

Check the box to turn off the automatic padding.

Troubleshooting

If the preheader is not appearing, check the HTML of the message. There must be a valid <body> tag in the actual message. The preheader is placed after the body tag during merge.

If the body tag is in a dynamic block, or is commented out, merge will not see the <body> tag and the preheader will not be inserted.

Testing for the Most Effective Combination of Subject Line and Preheader

The Preheader is supported for Cells and Splits campaigns, and it is on the Comparisons report after “Subject.”

By using the subject field, the preheader field, and the Projected Open Rate in testing and on the Comparisons report, you will then be able to do Subject Line / Preheader Pair Testing to quickly determine the pair that was most successful working together for creating opens.

The Projected Open Rate is not affected by Apple MPP and is the only open metric that can be used to accurately test and compare open rates after August, 2021.

How Do I Add and Test Preheaders in Cells and Splits Campaigns?

After adding preheaders to cells, select both Subject Line and Preheader to determine and use the combination of subject line and preheader text that produced the highest Projected Open Rate. You can learn more about the Projected Open Rate here.

If you wish, you can copy a preheader into child cells.

How Do I Add Preheaders to CSV Imports for Cells and Splits?

You can include preheaders in cells and splits campaigns that are uploaded by CSV.

If you have padding HTML in your template, you will want to deactivate the padding that automatically follows the preheader by entering a 1 in the column after the preheader column. See the example below.

How Do I Identify the Best Performing Subject Line and Preheader Pairs in Reports?

The preheader appears on the Comparison Report, after the Subject Line field. The row with the highest Projected Open Rate will indicate the combination of Preheader and Subject Line that produced the highest open rate, without noise from Apple MPP. Use only the Projected Open Rate when comparing open rates across cells or campaigns.

Appendix

More Resources:

How Does the Preheader Work?

When you add a preheader, during the merge, a span is inserted after the email’s <body> tag. The span contains the preheader and personalized content, and CSS styling to make it invisible in the opened email.

The preheader is followed by a calculated length of non-collapsible padding to prevent the first visible email text from following the preheader into the inbox preview. The padding is invisible in the opened email, just like the preheader itself.

What is Smart Padding?

Shorter preheaders can have a bigger impact, but without padding will be closely followed in the preview by the first visible text from the email. Too much padding wastefully increases email size.

Cheetah Messaging uses Smart Padding, which considers the lengths of both the subject line and the preheader to calculate the perfect amount of padding, for both:

The Gmail and Yahoo browser inboxes which place the preheader on one line following the subject line, and in
Typical mobile app inboxes which place the preheader on typically two lines under the subject line

Smart Padding prevents unneeded HTML from being added to the email.

Understanding Open Metrics

You can test the effectiveness of preheaders and subject lines alone and in combination using open rates.

It is important to understand open rates post Apple MPP, and be able to identify what can and cannot still be reliably used to compare open performance in multivariate tests and across campaigns.

The table below is a glossary of open metrics used in Cheetah Messaging, with call-outs to metrics common in other platforms you may also use, and if there are differences.

Reporting Term	Definition	Can be used to compare open rates across cells or campaigns
Projected Open Rate	The unique human open rate of just the recipients whose opens or non-opens would be visible. You will find this metric available anywhere in Cheetah Messaging where open rates would logically be compared.	Yes. This is the only open rate that enables you to compare open rates across cells or campaigns after August, 2021. It is used in Cheetah Messaging reports and multivariate tests as the only recommended open rate comparison metric.
Pre-cached Opens	The percent of recipients of the campaign or cell who are using Apple MPP - expect this to vary, sometimes significantly, across testing cells or campaigns due to mailing list and segment variances. This metric is present in platforms that address Apple MPP opens, and is usually determined through a generic user agent, which counts some real opens as false. Cheetah Messaging compares opens to IP addresses that are updated twice-weekly for more precise identification.	No. This segment is confirmed live email addresses and is typically filtered or exported by users for focused engagement.
Are Real Sometimes called Unique Human Open Rate or Filtered Open Rate in other platforms	The unique human open rate in the campaign, without machine opens, as a percent of all delivered emails. Note: If you use multiple platforms or have migrated to Cheetah Messaging from another platform, this is the metric you will be accustomed to, as it is the open rate that email platforms across the industry typically offer to help users understand open rates post Apple MPP. We strongly recommend that it not be used for any comparison purposes for campaigns sent after August, 2021.	No. Different campaigns and cells usually have different ratios of Apple MPP users and non-users. And, this percentage is based on the total delivered, which includes recipients whose opens or non-opens cannot be seen but are regardless counted as not opened. An analogy would be if a survey were sent out asking for preferences of the color red, or green, and all the recipients that didn’t respond were put down as having answered “green.” It is not valid for any comparison purposes for campaigns sent after August, 2021.
Real Readers	The number of humans that visibly opened the email, it includes human clicks (non-bot) as an indicator of open when there was no visible open due to precaching. Platforms that address Apple MPP will have a similar metric. Most platforms will not include clicks, and will not have bot clicks removed.	No. Because different campaigns and cells have different ratios of Apple MPP users and non-users, it is not valid for comparison purposes.
Total Open Rate, AKA Unique Open Rate	All unique opens, human and machine, as a percent of all delivered emails. We strongly recommend that it not be used for any purposes for campaigns sent after August, 2021.	No. This metric is inflated by machine opens and does not adjust for data hidden by Apple MPP. It is not valid for comparison purposes.
Pre-Cached Opener is also a Real Reader	Recipients that use Apple MPP, and were precached, but who also visibly interacted with the email.	No, these are the Apple MPP users who clicked in any client or opened outside of the Apple Mail app.

Adding and Editing Preheaders Using APIs

You can add and edit preheaders using the current APIs for campaign creation, and toggle off and on the automatic padding that follows the preheader.

See: