Email Preheader Preview
Type your from-name, subject, and preheader. See exactly how the email renders in Gmail Desktop, Gmail Mobile, Apple Mail, and Outlook inbox lists.
Inbox previews
What is a preheader and why does it lift opens 8 to 12 percent?
The preheader is the snippet of text that appears next to or beneath the subject line in inbox lists. Most clients pull the first 80 to 110 characters of the email body if you do not set a preheader explicitly. That default usually shows "Hi there," or "View this email in your browser" or the start of your signature. All wasted.
Setting an explicit preheader (via a hidden span with display:none at the top of your HTML, or via your ESP's preview-text field) gives you a second subject line. Studies across millions of cold-email sends show preheader-optimized emails open 8 to 12 percent better than emails using the default body-snippet fallback.
Preheader length by client
Gmail Desktop: shows 80 to 100 characters next to the subject. Anything past gets truncated with an ellipsis.
Gmail Mobile: shows up to 2 lines of preheader text under the subject, roughly 80 to 130 characters depending on screen width.
Apple Mail iOS: combines subject + preheader into a single preview block of 2 lines. The subject takes priority; preheader fills whatever space is left.
Outlook Desktop: shows roughly 50 to 80 characters of preheader, with the cutoff varying by inbox column width settings.
Safe range: 35 to 90 characters works across every major client. Under 35 leaves the preview area looking sparse. Over 110 reliably truncates on mobile.
Writing preheaders that get opens
Treat the preheader as a complement to the subject, not a repetition. The subject hooks; the preheader expands. If the subject is "Quick question, Sarah" the preheader should give the question's substance, not the same words again.
Patterns that consistently work: 1) Specific detail that adds curiosity ("about your Series B announcement"). 2) A short value clue ("3-min loom on your homepage CRO"). 3) Acknowledgment of context ("saw your post on inbox warm-up"). 4) Personalization variable ("{{company}} is hiring 12 SDRs"). Combine personalization in both subject and preheader for the strongest open lift.
Common preheader mistakes
Mistake 1: leaving it blank. The default fallback (first body line) is almost always wasted real estate. Always set the preheader explicitly.
Mistake 2: too long. Anything past 110 characters truncates on mobile, which is where 67 percent of B2B email is opened. Aim for 35 to 90.
Mistake 3: repeating the subject. Doubles your hook word count but adds zero information. Worse opens than just the subject alone.
Mistake 4: ALL CAPS or excessive punctuation. Inbox preview rendering is tiny; caps and !!! read as shouting at a glance and depress opens.
Mistake 5: forgetting the variable interpolation. A literal {{first_name}} in the preheader (because your ESP did not render it) is an instant credibility kill.
Frequently asked questions
Is this preheader preview tool free?
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Yes, completely free with no signup. Type your fields, see the rendered preview in real time across 4 major inbox clients.
What is a preheader in an email?
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The preheader (also called preview text) is the snippet shown next to or below the subject line in inbox lists. It is set either via a hidden HTML element at the top of the email body or via your ESP's preview-text field.
How long should an email preheader be?
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35 to 90 characters works across every major client without truncation. Gmail Desktop and Outlook truncate around 80; Gmail Mobile and Apple Mail show up to 130. Optimize for the shortest, which is Outlook.
How do I set a preheader in HTML email?
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Add a hidden span at the very top of your HTML body: <span style="display:none; max-height:0; overflow:hidden">Your preheader text</span>. Most ESPs (SendGrid, Mailchimp, ConvertKit, Customer.io, HubSpot) also provide a preview-text field that does this automatically.
Does the preheader affect deliverability?
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Indirectly. Spam triggers in the preheader count toward your overall content score the same as triggers in the subject or body. Keep the preheader free of spam words (FREE!, GUARANTEED, ACT NOW) just like the rest of the email.
Why does my preheader show the wrong text?
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Most likely your HTML preview span is not at the very top of the body, or it lacks the display:none and max-height:0 CSS. The order of HTML matters: the preheader span must come before any other visible content. Re-check the order in your template.
Can I use emoji in the preheader?
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Yes but be careful. Emoji render inconsistently across clients (Gmail and Apple Mail show them; older Outlook versions show squares). Keep emoji count to 0 or 1 for cold outbound; higher counts read as marketing spam to filters and humans alike.
Does the preheader help if my open rate is low?
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Yes by 8 to 12 percent on average when moved from no preheader to an optimized one. The lift comes from giving readers a second hook to decide whether to open. It cannot fix bad sender reputation or wrong audience targeting; those are separate problems.
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