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Email preheader text is the short line of text that appears after the sender name and subject line in an inbox list, and it is one of the first things a subscriber reads before deciding whether to open. It sits inside your wider email marketing programme, and it is one of the few settings that costs nothing to change and takes minutes to fix.
Published length ranges differ from guide to guide, and a single number cannot settle it because inboxes disagree: Klaviyo's own help centre documents a visible range from 34 characters on Gmail iOS to 236 on Outlook.com. This post shows how to write for that range, where to type the line in Mailchimp, Klaviyo and Omnisend, and how to test it without trusting open rates.
Quick Answer
Email preheader text is the preview line beside your subject line. As a working rule, put the one fact that earns the open in the first 30 characters, finish the thought by about 80, and write it as a second line that adds to the subject instead of repeating it. If you leave it blank, the inbox fills the space with whatever sits at the top of your email, such as alt text or a navigation bar.
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Email Preheader Text: What It Is and Where It Appears
A preheader is the preview snippet that an inbox displays next to or under the subject line, and you control it with a dedicated field in your email platform. Mailchimp defines it as "the text to the right of the subject line that gives a brief preview of the email". Many platforms and developers call the same thing email preview text, and the two terms are interchangeable.
The sender name, the subject line and the preview line form one unit in the inbox list. ActiveCampaign describes the preheader as working like a "second subject line", which is a useful way to plan it: the subject line makes a claim, and the preview line supplies the detail that makes the claim worth checking.
How Many Characters of a Preview Actually Show?
Anywhere from 34 to 236 characters of a preview can show, depending on the inbox app, so a safe design puts the essential words first and treats the rest as a bonus. Published guidance gives ranges rather than a limit: Mailchimp suggests keeping a preheader between 30 and 80 characters, even though it notes preheaders are typically about 85 to 100 characters long, because the shorter range fits more devices. ActiveCampaign notes that most mobile preheader text is between 30 and 55 characters long.
The sharpest data point comes from Klaviyo's help centre, which lists 34 characters on Gmail iOS and 236 on Outlook.com and adds that these counts are examples, not fixed limits.
Plan for the short end until your own data says otherwise. We did not find a South African split of email opens by device or inbox app, so the only local context is that DataReportal counted 127 million active cellular mobile connections in late 2025, equal to 196 percent of the population. That is connections, not email readers. Check the device and inbox-app split in your own platform's reports before you decide how much desktop room to count on.
Worked example: front-load to survive a 34-character cut
Sample preheader: Free delivery ends Sunday. Order by 23:59 and we ship Monday. That is 61 characters in total (this is sample copy, not a client result).
The first sentence, "Free delivery ends Sunday.", is 26 characters. A 34-character view shows "Free delivery ends Sunday. Order b", so the offer and the deadline both survive the cut and only the detail is lost. Reverse the order ("Order by 23:59 and we ship Monday. Free delivery ends Sunday.") and the same cut keeps the 23:59 deadline but hides the free-delivery offer and its Sunday end date.
Preheader text length in one paragraph
Preheader text length is a range, not a number: published guidance runs from 30 to 80 characters (Mailchimp) up to 40 to 130 (ActiveCampaign), and Klaviyo documents 34 characters on Gmail iOS. Write the deciding fact into the first 30 or so characters, finish the sentence by about 80, and test in the inbox apps your own subscribers use.
What Shows When the Preview Line Is Left Blank
When you set no preview line, the inbox builds one for you from the first readable text in the email, and that text is rarely what you would have chosen. Klaviyo states that "if you do not set preview text, inboxes automatically pull it from the beginning of your email" and that this can include image alt text or your navigation bar. ActiveCampaign makes the related point that a preview line that is too short can also be topped up with text from the start of the email.
Subject: "Our October newsletter". Preview: whatever is at the top of the template. The subscriber sees a navigation menu or a logo's alt text next to a generic subject, and nothing that gives them a reason to open.
Same subject, deliberate preview: "Our October newsletter" / "Three supplier price changes and the stock we are clearing before month-end." The subject names the format and the preview names the contents, so the two lines together do what neither does alone.
Litmus adds a stronger warning for HTML builds: email clients pull in enough characters to fill all the available preview space, up to five lines. A short preheader without padding can therefore be followed straight away by body text, which is the cue to use the hidden-preheader method covered below.
Subject and Preview Pairs You Can Adapt
How to write preheader text comes down to one rule: the preview line must add a fact, a deadline or a next step that the subject line does not already carry. These preheader text examples are sample copy written for typical South African sends, so adjust the details to your own offer.
| Send type | Subject line | Preview line | Best for |
|---|---|---|---|
| Weekend sale reminder | Last call before the weekend | Free delivery ends Sunday. Order by 23:59 and we ship Monday. | Stores with a hard deadline |
| Welcome email | Welcome. Your first-order code is inside | Paste it at checkout. Here is exactly where it goes. | New subscribers, see our welcome email sequence |
| B2B newsletter | Month-end close checklist for finance teams | A one-page list to print and tick off. No sign-up needed. | Professional services and B2B lists |
| Order confirmation | Your order is confirmed | Courier collection is booked. A tracking link follows once it ships. | Transactional sends, see transactional email in South Africa |
Notice what each preview line does: it gives a deadline, a location, a limit on effort or a status. None of them repeats the subject. If your cold outreach is the use case, the subject line carries more of the weight, and our guide to B2B cold email subject lines covers that side.
Where to Set the Preview Line in Mailchimp, Klaviyo and Omnisend
Every major platform has a dedicated preview field, and the only place it gets complicated is a custom HTML template, where the text has to sit at the very top of the code. The table below records where each platform's own documentation puts the field, as read in October 2026.
| Platform | Where you set it | Watch for |
|---|---|---|
| Mailchimp | Campaigns, then All Campaigns, then edit the Subject section, which holds both the subject line and the preheader | Mailchimp suggests 30 to 80 characters |
| Klaviyo (drag-and-drop) | Open the campaign, go to the Message step and fill the Preview text field | Documented range of 34 to 236 characters by inbox app |
| Klaviyo (custom HTML) | Insert the preview text at the beginning of the email's code | Test it, because the inbox otherwise falls back to the top of your template |
| Omnisend | Step 1, Email Settings, next to the subject line and sender details | Omnisend describes it as text to "add context or urgency" |
If you build your own HTML, the established technique is a hidden block placed before the visible content. Litmus publishes it as a div styled display: none; max-height: 0px; overflow: hidden; that holds the preview text, followed by a second hidden div of padding characters (zero-width non-joiners and non-breaking spaces) so that body copy does not slide into the preview. Litmus describes this as a progressive enhancement that some inbox apps will ignore, so verify it in the inbox apps your list uses.
Setting a preview line in one paragraph
In Mailchimp, Klaviyo's drag-and-drop editor and Omnisend, the preview line is one text field in the campaign setup step, next to the subject line. In custom HTML you place it at the top of the code and, if you want to stop body text following it, add padding characters after it.
Template design affects all of this, because a logo or menu at the very top is what an unset preview falls back to. Our guide to email design in South Africa covers how to structure the top of a template so the fallback is harmless.
How to Test a Preview Line Without Trusting Open Rates
A preview line test should be judged on clicks, because open rates are distorted for subscribers on Apple Mail. Mailchimp's own FAQ says that "with Apple MPP enabled, emails present in Apple Mail are reported as 'opened,' regardless of the contact's activity", and that click activity and click rate are still reported for Apple Mail contacts.
That changes how you read a subject-and-preview split test. A variant that "wins" on opens may simply have reached more Apple Mail users in one half of the split. Compare click rate per delivered email instead, and only call a winner when the list is big enough for the difference to mean something; on a small list a gap between two variants is noise with a story attached. Our guide to email A/B testing in South Africa sets out how to run that split properly.
- Change only the preview line and keep the subject, sender name and send time identical.
- Send the test to a random split, not a first-half and second-half cut of an alphabetical list.
- Judge on click rate per delivered email, then check revenue or enquiries where your platform tracks them.
- Send a test to your own accounts in Gmail, Apple Mail and Outlook to check the visible cut-off by eye before the real send.
Want a clean test set up before your next send?
Tell us your list size and platform and we will tell you whether a split test is realistic at your volume, and how to run it.
Preview Line Mistakes to Fix First
The most common preview-line mistakes are repeating the subject, leaving the field to the fallback and burying the point after the first 40 or so characters.
Repeating the subject. "Last call before the weekend" followed by "Last call before the weekend, don't miss out" wastes the second line. Use it for the deadline, the offer terms or the next step.
"View this email in your browser" as the preview. If a template opens with that link and no preview line is set, an inbox can pull it in as the preview, which says nothing about the message and suggests the email may not render properly.
Burying the point after the 40th character. A long lead-in such as "We hope you are well and wanted to tell you about..." pushes the useful words out of a short mobile view.
Two more habits to drop: using the preview for a clickbait question the email never answers, and forgetting to update it when you duplicate last month's campaign. When you duplicate last month's campaign, check that the preview line was updated as well. Deliverability sits upstream of all of this, since no preview line helps an email that lands in spam, which is the subject of our email deliverability guide.
Why South African Businesses Choose Growth Pulse Media
Growth Pulse Media is a Johannesburg agency founded by Dirk van Greuning, who built and scaled a large South African ecommerce business before founding it. We are a Registered Shopify Partner and an Omnisend Certified Partner, all work is executed in-house and we keep a limited client load so each account gets senior attention.
For stores running campaigns and flows on Omnisend, the preview line is one of the first things we review, alongside subject lines, segmentation and sender reputation. You can see how that sits within a wider build on our email marketing service page, and a free audit is the quickest way to find out what your inbox is showing today.
Who This Is NOT For
Senders hoping a preview line will fix a weak list. A better preheader sharpens a good email, but it does not repair a stale list or a spam-folder problem. Fix list quality and authentication first.
Very small lists expecting a clear split-test winner. With a few hundred subscribers, the click difference between two preview lines is mostly chance. Write the best line you can and revisit once the list grows.
Anyone planning to put legal or consent wording in the preview line. A preheader is a teaser, not a notice. Sender identification and opt-out belong in the email itself and in your consent process, covered in our email marketing compliance guide.
Want us to look at your whole campaign setup?
Send us your platform name and one recent campaign and we will review subject, preview line and top-of-template together.
Frequently Asked Questions
What is email preheader text?
Email preheader text is the short line of preview copy that appears after the subject line in an inbox list. Mailchimp defines the preheader as the text to the right of the subject line that gives a brief preview of the email. You set it in a dedicated field in your email platform.
How long should preheader text be?
Published guidance ranges from 30 to 80 characters (Mailchimp) to 40 to 130 (ActiveCampaign), and Klaviyo documents as few as 34 characters visible on Gmail iOS. Put the key words in the first 30 or so characters and treat anything beyond that as a bonus for wider screens.
What happens if I do not set preheader text?
The inbox pulls preview text from the beginning of your email. Klaviyo notes that this can include alt text or a navigation bar, so the subscriber may see something unrelated to your message.
Should the preheader repeat the subject line?
No. ActiveCampaign advises against repeating the subject line and suggests making the two work together. Use the preview line for the detail the subject leaves out, such as a deadline, an offer condition or the next step.
How do I test which preheader works better?
Run a random split that changes only the preview line and judge it on click rate, not open rate. Mailchimp's FAQ says Apple Mail Privacy Protection reports emails as opened regardless of what the contact did, while click activity is still reported.
Get your campaigns reviewed by an operator
We work with Shopify stores and Omnisend email programmes, and we will review your subject lines, preview lines and campaign setup. No obligation, and we will get back to you within 24 hours.
