Updated · 7 min read
Preheader text: the second subject line most programs ignore
Preheader text is free real estate and most programs give it away. Picture your own inbox right now: every message has a subject, and right next to it (or just underneath, on mobile) a second line of grey text — that's the preheader. Another 50 to 100 characters to sell the open, served up by every major inbox client, and the default output is usually 'View this email in your browser' or whatever alt text happened to sit at the top of the HTML. The subject line is the headline. The preheader is the subhead. Write them as a pair or don't bother sending.
By Justin Williames
Founder, Orbit · 10+ years in lifecycle marketing
The grey line nobody wrote on purpose
Open Gmail on your phone. Every email shows three things in the list: sender, subject, and a third line in lighter grey that finishes the pitch. That third line is the preheader — the first chunk of text in your email body that the inbox surfaces as a preview. Every major client renders it: Gmail desktop shows around 90 characters, Gmail mobile shows about 40, Outlook shows 50, Apple Mail shows up to 140. The client just grabs whatever preview-eligible text it finds first in your HTML.
If you don't set the preheader explicitly — most ESPs (the platform that sends your email — Braze, Klaviyo, Customer.io, Mailchimp, the lot) have a dedicated field for it right next to the subject — the client will invent one. Usually it grabs the alt text on your logo, or the "View in browser" link your template inherited from 2017. Neither earns anyone's attention.
The subject line is the headline. The preheader is the subhead. If your headline has to stand alone, you've halved the pitch.
Every serious ESP exposes the preheader field. Fill it in. Every time. Leave it blank and the client invents one, and the invented one is almost never the one you'd have chosen if you'd had three seconds to think.
One question that always comes up: does the preheader affect deliverability — your odds of landing in the inbox rather than spam? No, not directly. Mailbox filters care about subject, sending domain, authentication, body content. What the preheader does do is lift open rate, which feeds engagement signals, which affects deliverability over weeks and months. Second-order mechanism, real impact.
Subject and preheader are one move, not two
Write subject and preheader together. Not separately, not in two different sprints, not one by the copywriter and the other by whoever happened to be in the editor when it went out. The pair should function as a one-two punch — subject hooks, preheader expands.
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The shape: subject raises the question, preheader answers half of it, the remaining half is the click. Or the subject teases the outcome and the preheader adds the specific detail that makes it concrete. Either way, they're written in one sitting, not two.
Transactional — order confirmations, shipping notifications, password resets, the operational stuff your platform fires automatically — is where this matters most, and where most programs ignore it hardest. "Your order shipped" plus "Arriving Thursday. Track it here." is immediately useful. "Your order shipped" plus "View in browser" is actively user-hostile. Transactional opens at 3–5x the rate of marketing — the preheader is often the summary a user doesn't even need to open the email to use.
The four ways programs waste the slot
Repeating the subject.Inbox scanners read subject + preheader together as one line. If the preheader just restates what the subject said, you've wasted the slot and signalled that nobody was paying attention at send time. "Your order shipped" followed by "Your order has shipped." reads as effort taken and wasted.
Leaving hygiene text in."View this email in your browser." "Trouble viewing? Click here." Artifacts of a pre-responsive era — the years before phones started rendering email properly — that somehow never got removed from the template. The preheader slot is worth more than the web-version link, several orders of magnitude more.
Stacking emoji as filler.Preheaders front-loaded with star-sparkle-gift and no substance read as spammy and test badly every time. Emojis work sparingly as visual anchors. They don't work as the content itself — the reader is scanning for meaning, and meaning is not a party-popper.
Trusting the body's first line.Leave the preheader field blank and the client invents something. Usually "[Your Brand] Logo" alt text or a preview-text hack your template inherited from 2017. Neither sells the open. Both embarrass the program.
One more tactic worth retiring: padding the preheader with whitespace or zero-width characters to push hygiene text below the fold. That was a 2016 move. Modern clients have mostly stopped rendering trailing hidden content, and Outlook has a habit of displaying it anyway in ways that read as broken. Just keep the preheader short, intentional, and stop there.
Most of your audience reads forty characters
Write for mobile first. Gmail mobile truncates around 40 characters. Apple Mail mobile shows 60–80. Desktop clients show 90+. Which means your first 40 characters have to carry the whole message, with the next 50 as reinforcement for the desktop segment that gets the full reveal.
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The asymmetry is real and it's permanent: most of your audience sees the short version, a meaningful minority sees the long one, and you write for both in a single field. That's the craft.
Test the pair, not just the subject
Subject lines get A/B tested constantly — split the audience, send version A to half, version B to the other half, see which one wins. Preheaders rarely get the same treatment, which is the missed opportunity. Since they appear in the inbox as a pair, the preheader affects open rate almost as much as the subject does. Test them together when you can — a four-arm test of subject A/B crossed with preheader A/B — or at least test preheader variants against a fixed subject to isolate the lift.
The A/B testing playbook has the test-structure mechanics — sample sizes, what to do when arms split unevenly, when to call a result. A good preheader rewrite on a high-volume send typically lifts open rate 5–15%, which is a lot of incremental opens for an hour of writing.
treats subject + preheader pairing as the default output — you don't get a subject without a preheader suggestion attached, because the two were never meant to be separate in the first place.
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Frequently asked questions
- What is email preheader text?
- The snippet of text shown in the inbox preview immediately after the subject line. Gmail desktop shows about 90 characters; iOS Mail shows about 40; Outlook web shows about 100. When not set explicitly, mailbox providers pull the first visible text from the email — which often produces useless fallback like "View in browser" or "Hi First Name,". A good preheader extends the subject rather than duplicating it.
- How long should a preheader be?
- Match the most-restrictive client your audience uses heavily. If iOS Mail share is high, write for 40-character visibility. If desktop-dominant, 90 characters. The first 40 characters should carry the hook regardless — anything past 40 is a bonus for clients that show more.
- Should the preheader repeat the subject line?
- No. Repetition wastes the second line of inbox preview real-estate. The preheader's job is to EXTEND the subject: add a hook, specific detail, or reason to open. If the subject says "Your Tuesday delivery is out", the preheader should say "Arriving 2-4pm, leave in mailbox" — not "Your Tuesday delivery is out for delivery."
- How do I hide a preheader after the visible portion?
- Invisible spacer pattern: after the visible preheader text, add 100-200 characters of non-breaking space characters (Unicode U+00A0) inside a div with display:none or color:transparent. This prevents mailbox providers from pulling the first body text into the preview — forcing them to use only your declared preheader. Common implementation: a hidden div with display:none, font-size:1px, line-height:1px, max-height:0, max-width:0, opacity:0, and overflow:hidden.
- Does preheader text affect deliverability?
- Not directly — preheader is a display feature, not a trust signal. But a well-written preheader increases open rate, which increases engagement signals, which feeds reputation over time. Indirect but real. The bigger risk: auto-pulled preheader defaults ("View in browser") that look broken or spammy and depress opens.
This guide is backed by an Orbit skill
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