Preview text—the snippet that appears below your subject line in most email clients—gets truncated at wildly different lengths depending on where your subscriber opens it. Gmail on desktop shows roughly 100 characters. Outlook on Windows cuts off around 40. Apple Mail on iPhone displays up to 140 in portrait mode, less in landscape.
Most newsletter operators write preview text once and assume it renders consistently. It doesn’t. And because preview text directly influences open rates (some studies peg the lift at 8–12% when optimized), understanding how truncation works matters more than you’d expect.
Where the cuts happen
Desktop clients are the most forgiving. Gmail shows approximately 100 characters on a typical monitor width. Apple Mail on macOS displays around 90. Outlook 2019 and 2021 on Windows cut hard at 40–50 characters, depending on subject line length—they share a fixed pixel width, so a long subject line eats into preview space.
Mobile is tighter. Gmail’s mobile app shows 80–90 characters in portrait, less in landscape. Apple Mail on iPhone displays up to 140 characters in portrait but drops to 70–80 in landscape. Outlook mobile sits around 65 characters regardless of orientation.
The problem: if your key message or call-to-action lives past character 50, roughly 30–40% of your list won’t see it. Outlook desktop users and anyone reading in landscape mode get cut off mid-sentence.
Frontloading vs. padding
The common advice is to frontload value—put your hook, offer, or call-to-action in the first 40 characters. That works when you have a single, clear message. “Early access ends Friday” or “Three new case studies inside” fit cleanly.
But frontloading creates a new problem: preview text that repeats your subject line. If your subject is “Case studies: how three operators doubled revenue” and your preview is “Three new case studies inside,” you’ve wasted 30 characters saying the same thing twice. Subscribers who do see the full preview get redundancy instead of context.
A better approach: use preview text to extend or qualify the subject line, but assume only the first 40–50 characters will render universally. Structure it so the opening phrase stands alone, and anything past character 50 adds detail for clients that display more.
Example: Subject line is “Affiliate link cloaking breaks in three places.” Preview text could be “DNS propagation, cache headers, redirect chains—here’s how to test each one.” The first phrase (“DNS propagation, cache headers, redirect chains”) gives context even when truncated. The second half (“here’s how to test each one”) adds value for subscribers on longer-display clients, but the preview still works without it.
Testing across clients
Most ESPs show a preview-text field in the send interface, but they don’t simulate truncation accurately. Beehiiv, MailerLite, and ConvertKit all display your full preview text in the editor—you won’t see how it renders on Outlook mobile until you send a test.
The best workflow: send test emails to multiple addresses on different clients before publishing. At minimum, check Gmail desktop, Apple Mail on iPhone, and Outlook on Windows. If you’re running a paid newsletter or sending to a B2B audience, add Outlook mobile to the rotation—corporate subscribers skew heavily toward Microsoft clients.
For operators sending daily or multiple times per week, set up a permanent test list with addresses tied to each major client. Send every issue to that list five minutes before the main send. Open each one, screenshot the inbox view, and compare truncation points. It takes three minutes and catches preview-text issues before they hit your full list.
When preview text doesn’t matter
Preview text has diminishing returns in three scenarios. First: if your open rates are already above 50%, you’re likely serving a highly engaged list that opens based on sender name and subject line alone. Optimizing preview text might add a percentage point or two, but it’s not your leverage point.
Second: transactional emails. Password resets, order confirmations, and receipt emails get opened regardless of preview text. If you’re using Postmark or a dedicated transactional service, default preview text (often the first line of body copy) works fine.
Third: emails where the subject line is self-contained and actionable. “Your invoice is ready” or “You’re confirmed for Friday’s workshop” don’t need preview-text reinforcement. Adding “Click here to download” or “See you at 2pm ET” is redundant.
Preview text matters most when your subject line raises a question or teases value without fully delivering it. If the subject is “Three underused features in your analytics dashboard,” preview text like “Session replay, funnel drop-off alerts, and cohort comparison—most operators miss all three” gives just enough detail to justify the open.
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