Email subject line checker

Keep it under 40 characters if you want it to survive on mobile inboxes like Gmail — Mobile, which truncates around 40 characters. Desktop clients are more forgiving, with Gmail — Desktop allowing around 70 and Apple Mail on iOS around 90 before truncating.

Preview text, also called a preheader, is the snippet of text shown after the subject line in most inbox list views. It's usually pulled from the first line of your email body unless you set it explicitly with a hidden preheader snippet — and it's prime real estate to add context the subject line couldn't fit.

Truncation is driven by pixel width, not a fixed character count — the limits shown here are practical character approximations. Screen size, font, sender name length, and whether icons or badges appear next to the subject all affect exactly where a client cuts off the text.

No. Preview text is most effective when it adds new information or a call to action that extends the subject line rather than repeating it — recipients scan both together, so redundant preview text wastes that visible space.

Not necessarily, but if the key words get truncated before the reader sees them, you lose their impact. Front-load the most important words and check how the subject renders on mobile, since that's where truncation is most aggressive.