How long should a subject line be (character limits across clients)?

Subject line length affects what recipients see across devices and email clients. Mobile screens typically show 30-40 characters, desktop webmail shows 60-70, and desktop clients vary by pane configuration. Anything beyond visible characters gets truncated with ellipsis.

Optimal length recommendations: Front-load key information in the first 30-40 characters—assume mobile truncation. Keep it under 50 characters for broad visibility. Use preheader text to extend your message rather than cramming everything into the subject. There's no perfect length—test with your audience.

Clarity beats length rules. A 60-character subject that communicates perfectly is better than a 30-character one that's unclear. Write the subject your message needs, then consider truncation. If essential information would be cut on mobile, rewrite to front-load it. Preview in multiple clients before sending to see exactly what recipients will see. The goal isn't minimum characters—it's maximum comprehension within visible space.