· 7 min read
Preheader text: the second subject line most programs ignore
The preheader is free real estate. It sits next to the subject line in Gmail, Outlook, Apple Mail, and every modern inbox client, and it gives you another 50–100 characters to sell the open. Most programs waste it on pre-header hygiene junk like 'View in browser' or the first line of their email's header content. Here's how to treat it as the second subject line it actually is.
Justin Williames
Founder, Orbit · 10+ years in lifecycle marketing
What the preheader actually is
The preheader is the first chunk of plain text in your email that shows up in the inbox preview. Every major client displays it: Gmail on desktop shows around 90 characters, Gmail mobile shows about 40, Outlook shows 50, Apple Mail shows up to 140. The client pulls it from the first preview-eligible text it finds — and if you don't explicitly set it, it'll grab whatever's at the top of your HTML body (often your logo alt text or a "view in browser" link).
The subject line is the headline. The preheader is the subhead. If your headline has to stand alone, you've halved the pitch.
Most ESPs (Braze, Customer.io, Iterable, etc.) have a dedicated "preheader" field in their email editor. Fill it in. If you don't, the client invents one for you, and the invented one is almost never the one you'd choose.
The pattern that works: subject + preheader as a unit
Write subject and preheader together, not separately. The pair should function as a one-two punch — the subject hooks, the preheader expands.
,
The pattern: subject raises the question, preheader answers half of it, leaving enough curiosity to earn the click. Or subject teases the outcome, preheader adds the specific detail that makes it concrete.
What to avoid
Don't repeat the subject.Users scanning the inbox see subject + preheader together. If the preheader just restates what the subject already said, you've wasted the slot. "Your order shipped" followed by "Your order has shipped." reads as lazy.
Don't use hygiene text."View this email in your browser", "Trouble viewing? Click here" — these are artifacts of a pre-responsive email era. The preheader slot is worth more than the web-version link.
Don't use emoji-heavy filler.Preheaders with ⭐✨🎁 and no substance read as spammy and don't test well. Emojis can work sparingly as visual anchors; they don't work as the content itself.
Don't rely on the body's first line.If you leave the preheader field blank, clients pull whatever text appears first in your HTML. That's usually "[Your Brand] Logo" alt text or a preview-text hack your template inherited. Neither sells the open.
Length and device considerations
Write for mobile first. Gmail mobile shows roughly 40 characters before truncating; Apple Mail mobile shows 60–80; desktop clients show 90+. Your first 40 characters have to carry the message.
,
Don't pad preheaders with whitespace or zero-width characters to push hygiene text below the fold. That was a 2016 tactic; modern clients have largely stopped displaying trailing hidden content, and it risks rendering oddly in Outlook.
Testing and iteration
Subject lines get A/B tested constantly; preheaders rarely do. That's a missed opportunity — because they appear as a pair, the preheader affects open rate almost as much as the subject. Test them together when you can (4-arm test: subject A/B × preheader A/B) or at least test preheader variants against a fixed subject to isolate the lift.
The A/B testing playbook covers test structure. A good preheader rewrite on a high-volume send typically lifts open rate 5–15% — worth spending an hour on.
covers subject + preheader pairing as its default output — you don't get a subject without a preheader suggestion.
Frequently asked questions
- How long should my preheader be?
- Write the complete thought in the first 40 characters (mobile truncation). Use the next 50 for reinforcement that desktop users will see. 90 characters total is the usable zone; anything past that is effectively invisible.
- Should subject and preheader say different things?
- Yes — they should function as headline and subhead. The subject hooks, the preheader adds the specific detail or answer that earns the click. Restating the subject is the most common preheader mistake.
- What if I leave the preheader field blank?
- The email client will pull the first preview-eligible text in your HTML body — usually logo alt text or a 'view in browser' link. Neither sells the open. Always populate the preheader field explicitly.
- Can I hide promotional text after the preheader to keep it clean?
- That was a 2016 tactic using whitespace or zero-width characters to push hygiene content below the fold. Modern clients have mostly stopped rendering hidden trailing content, and Outlook can display it unpredictably. Just keep the preheader short and intentional.
- Do preheaders matter for transactional emails?
- Yes — especially for transactional. 'Your order shipped' + 'Arriving Thursday. Track it here.' is immediately more useful than 'Your order shipped' + 'View in browser'. Transactional emails get opened at 3–5× the rate of marketing; the preheader is the summary a user often doesn't need to click past.
- Should I use emojis in the preheader?
- Sparingly, as visual anchors rather than content. Emoji-heavy preheaders (⭐✨🎁) read as spammy. A single emoji that reinforces the message can help inbox scannability; a string of them looks like filler.
- Does preheader affect deliverability?
- Not directly — mailbox filters look at subject, sending domain, authentication, and body content. But indirectly it affects open rate, which affects engagement signals, which affects future deliverability. A better preheader lifts opens, which protects reputation over time.
Related guides
Email dark mode: the four render modes and how to not break any of them
Dark mode in email isn't one thing — it's four different render behaviours depending on the client. Design without knowing which mode you're hitting and your emails will look broken to 40% of your audience. Here's what each client does.
Mobile email design: 65% of opens are on a phone — design for that
Two-thirds of email is opened on mobile. Most email designs still start with a desktop layout and hope it collapses well. Here's the mobile-first rules that reliably produce emails that read, click, and convert on a phone.
Email accessibility: the seven rules that make your emails readable by everyone
Email accessibility isn't a compliance tax — it's the difference between reaching 100% of your audience and the 85% who have easy sight, steady hands, and full-volume screens. Here are the seven rules that cover 90% of what actually matters.