Email Marketing

Subject Lines & Preview Text for Mobile — The Complete 2026 Optimisation Guide

What Is Preview Text and Why It Matters as Much as the Subject Line

Preview text — also called the preheader — is the snippet of text that appears next to or below your subject line in the inbox list view. Most email clients automatically pull this from the first line of your email body unless you explicitly set it. Left unconfigured, this often shows unhelpful text like "View this email in your browser" or a jumble of unsubscribe links, wasting valuable inbox real estate that could be driving opens.

Character Limits by Mail Client and Device (2026 Data)

Space allowances vary meaningfully across clients. On iPhone Mail, subject lines display roughly 33-43 characters before truncating, with an additional 40 characters of preview text visible. On Gmail's Android app, subject lines show approximately 30 characters with 40 more of preview text. On Gmail desktop, subject lines can display up to 60-70 characters, with 80-100 characters of preview text visible depending on browser window width. Outlook desktop shows around 60 characters of subject line and limited preview text depending on the reading pane configuration.

How to Set Preview Text Manually

Most email platforms including Mailchimp, Brevo and Klaviyo allow you to manually set preview text separately from your email body content. This is one of the most underused features in email marketing — setting a deliberate preview text that complements rather than repeats your subject line can meaningfully increase open rates.

The most effective approach is to treat the subject line and preview text as two parts of a single message. If your subject line creates curiosity, use the preview text to add a supporting detail that increases the pull to open. If your subject line states a benefit, use the preview text to add specificity or urgency that the subject line didn't have room for.

Subject Line + Preview Text Pairing Examples

A subject line like "Your cart is waiting" paired with preview text "Free delivery ends tonight" together create a complete, compelling message that neither line achieves alone. A subject line like "3 changes to make this week" paired with preview text "Takes less than 10 minutes" adds a low-effort reassurance that increases the likelihood of engagement.

Avoid the common mistake of simply repeating your subject line's message in the preview text — this wastes the additional space rather than building on it. Also avoid leaving preview text to default to your unsubscribe link or "view in browser" text, which happens automatically if you don't set it manually and represents a significant missed opportunity.

Emoji Rendering Differences Across Mobile Platforms

Emoji appearance varies subtly between iOS and Android, and rarely renders identically to how it appears in your email editor. Always test your subject line with emoji on both an iPhone and an Android device before sending to your full list, since a broken or unexpected emoji rendering (showing as a box or question mark) can look unprofessional and reduce trust.

Testing Your Subject Line and Preview Text Combination

Before sending any campaign, send a test email to yourself and view it on both iOS Mail and Gmail's Android app — the two most common configurations for Indian subscribers. Check exactly where truncation occurs and confirm your most important message is fully visible before the cut-off point on both platforms.

Mobile Optimisation Checklist

• Front-load your most important words in the first 30-35 characters
• Always set preview text manually — never leave it to default
• Make preview text complement, not repeat, your subject line
• Test emoji rendering on both iOS and Android before sending
• Preview every campaign on mobile before sending to your full list
• Remember: 80%+ of Indian subscribers open on mobile devices