## The Line Under the Subject That Most Senders Waste Open any inbox and look at a message you have not read yet. You see the sender name, the subject line, and then a short line of grey text that continues the thought. That grey line is the preheader, also called preview text or the snippet. It is the second thing a subscriber reads before deciding whether to open, scroll past, or delete.
Many campaigns leave it to chance. When no preheader is set, the inbox simply pulls the first text it finds in the email. That is often "View this email in your browser," a logo's alt text, a navigation menu, or a string of tracking text that means nothing to the reader.
The result is a subject line doing all the work while a free piece of inbox real estate says "Having trouble viewing this message?" This guide explains what preheader text is, how inboxes decide what to show, how to write preview lines that support the subject line instead of repeating it, how to stop unwanted text from leaking into the preview, and how to test preheaders without fooling yourself with unreliable open data.
## What Preheader Text Is The preheader is the short summary text that email clients display next to or below the subject line in the message list. It is not a separate field in the email standard. Inboxes generate it by reading the beginning of the email body and showing as much text as fits.
That gives senders two options: - **Let the client guess.** The preview shows whatever text appears first in the HTML or plain-text body. - **Set it deliberately.** You place a short line of text at the very top of the email body so that it is the first thing the client reads. Most email builders and templates have a dedicated preheader or preview text field that does this for you.
A deliberately written preheader is usually hidden from the visible design of the opened email, or shown as a small line above the header. Either way, its main job happens in the inbox, before the open. ## Why the Preview Line Matters The subject line gets most of the attention in email marketing advice, and for good reason. But subscribers rarely read a subject line in isolation.
They scan sender, subject, and preview as one unit, often in under a second. The preheader influences that decision in several ways. ### It adds context the subject line cannot fit Subject lines are short, especially on mobile screens.
A preheader gives you a second line to explain the offer, name the deadline, or answer "why should I care?" A subject like "Your October report is ready" becomes far more useful with a preview such as "Delivery rate, top campaigns, and three routes worth reviewing." ### It signals legitimacy A clean, relevant preview reads like a message written by a real sender for a real recipient.
A preview full of broken template text, unrendered merge tags, or repeated legal boilerplate looks careless at best and suspicious at worst. Subscribers who do not trust a message are more likely to ignore it, and ignored mail is a weak engagement signal for inbox providers over time. ### It reduces mismatched expectations When the subject and preview together describe what is inside, the people who open are the people who wanted that content.
That tends to produce better downstream behavior: clicks, replies, and fewer complaints. A preheader that overpromises can win an open and lose the subscriber. ### It works even when the email is never opened A subscriber who reads "Sale ends Sunday at midnight" in the preview and does not open has still received your main message. For deadlines, reminders, and announcements, the inbox line itself can carry the point.
## How Email Clients Choose What to Show Every email client treats preview text a little differently, and the details change as clients update their apps. A few principles hold across most of them: 1. **The client reads from the top of the body.** It takes the first readable text in the email, in source order, not visual order.
Text that appears visually lower in the design but earlier in the HTML can end up in the preview. 2. **Length depends on the screen.** A wide desktop inbox can show a long line. A phone in portrait mode shows much less. The same email can display a full sentence in one client and a few words in another. 3.
**The subject line competes for space.** In layouts that show subject and preview on one line, a long subject leaves very little room for the preheader. 4. **Some clients show no preview at all.** Users can turn previews off, and some views, such as notification banners or compact list modes, trim or hide them. Because the visible length varies so much, write preheaders so that the first few words carry the meaning on their own.
Treat everything after that as a bonus for wider screens. ## Writing Preheaders That Earn the Open A good preheader does not repeat the subject line. It continues the sentence, answers the obvious next question, or adds a detail that makes the message more concrete. ### Complement the subject, do not copy it Repetition wastes space. If the subject is "Spring collection is here," a preview of "The spring collection is now available" adds nothing.
"Linen shirts, light jackets, and free returns through May" gives the reader new information. ### Lead with the most important words Since some clients cut the preview short, put the key benefit, number, or deadline first. "Ends tonight: 20% off annual plans" survives truncation better than "We wanted to remind you that our offer on annual plans ends tonight." ### Match the message inside The subject and preheader form a promise.
The email body should deliver it in the first screen. If the preview mentions a discount code, the code should be visible without scrolling. ### Use the subscriber's context, carefully Personalization can make a preview feel relevant: a first name, a city, a plan name, or the item left in a cart. Always set a fallback value so a missing field never produces "Hi ," or a raw merge tag like `{{first_name}}` in the inbox.
An unrendered tag in the preview is far more visible than one buried in the body. ### Keep the tone consistent with the sender A preheader that sounds nothing like your usual voice can feel off to regular readers. Match the style subscribers expect from your brand, whether that is direct, playful, or formal.
### Avoid spammy patterns The same writing habits that hurt subject lines hurt previews: all caps, strings of exclamation points, misleading "Re:" or "Fwd:" framing, and urgency that is not real. Clear, specific language usually performs better and reads as more trustworthy. ## Preheader Examples by Email Type The pairings below show how a preheader can extend the subject line for common campaign types.
| Email type | Subject line | Preheader | |---|---|---| | Promotion | 48 hours of free shipping | No minimum order. Ends Sunday at midnight.
| | Newsletter | This month in deliverability | Complaint rates, warmup plans, and a new checklist | | Product update | New: scheduled report exports | Get your weekly numbers by email, no login needed | | Abandoned cart | You left something behind | Your items are saved for 24 hours | | Event | Webinar seats are filling up | Thursday at 3 PM CET. Replay included for registrants.
| | Win-back | It has been a while | Here is what changed since your last visit | | Onboarding | Your account is ready | Three steps to send your first campaign | Notice that each preheader could be read on its own and still make sense. That is a useful test when the subject line is cut off or the reader skims.
## Stopping Unwanted Text From Leaking Into the Preview Even a well-written preheader can be undermined by what comes after it. If your preheader is short, many clients keep reading into the body to fill the remaining space.
That is how previews end up as "Free shipping this weekend View in browser | Unsubscribe | Home Shop About." ### Check what sits at the top of your template Look at the raw source order of your template, not just the design.
Typical culprits are: - "View in browser" or "Having trouble viewing this email?" links - Logo images with long alt text - Navigation menus and social icons - Hidden tracking or spacer elements that still contain text - Legal or compliance text placed in a top banner Move these below the preheader, shorten them, or remove them from the top of the template entirely.
### Fill the remaining space deliberately A common technique is to place invisible spacing characters after the preheader so the client has nothing meaningful to pull from the body. Many templates and email builders include this as an option. If you add it by hand, test it carefully across clients, because some characters render visibly in certain environments.
### Write a real plain-text version Some clients and many accessibility tools rely on the plain-text part of a multipart email. If your plain-text version starts with a long header or a tracking URL, that can show up in previews too. Make
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