Email Subject Line Tester

Aim for 30 to 45 characters, about four to nine words. Most phones show roughly 40 characters of the subject in portrait, and over half of email is opened on mobile. Longer lines aren't banned, but put the words that matter in the first 40 because the rest may never be seen.

Around 35 to 45 characters on iPhone and Android in portrait mode, depending on screen width, font size and the mail app. Desktop Gmail and Outlook show around 60 to 70 before cutting off. This tool marks the cut at 40 for mobile and 70 for desktop.

Avoid classic spam triggers like “free”, “act now”, “urgent”, “guaranteed”, “risk-free” and “congratulations”, plus anything in all caps and stacked punctuation like “!!!”. Avoid a fake “Re:” or “Fwd:” too: it's deceptive on a first email and people report it.

Usually, for cold and one-to-one email: a first name or company name signals the email was written for the reader. It only helps when the data is clean, though. A raw {{first_name}} tag or a wrong name does more harm than leaving it out.

One emoji can help a newsletter stand out in a busy inbox. In cold outreach it usually reads as marketing, and two or more look like a promotional blast. Some older clients also render emoji as empty boxes.

Preview text (preheader) is the line most inboxes show right after the subject. If you don't set it, the inbox pulls the first text in your email, often “Hi Alex,” or “View in browser”. Use it to say the next thing, not to repeat the subject.

A real, specific question works well because it opens a loop the reader wants closed and invites a reply. Generic ones like “Quick question?” have been overused in cold email and now read as a template.