Donaldson R F Email Subject Line Checker
Count the characters in your subject line, preview how it will look in the inbox — and where phones and desktop programs cut it off — and get quick improvement tips.
How long should a subject line be?
There is no exact rule, because how much of a subject is shown depends on the screen, the font and the email program. As a guide, phones show about 30–40 characters, Outlook and Apple Mail roughly 50–60 and Gmail on a wide screen about 70. Putting the important words first means they survive when the end is cut off, and 20–60 characters works well for most messages. The previews here are approximate, based on these typical limits.
Avoid ALL CAPS, repeated punctuation (!!!), and words strongly associated with spam. Do a final check for unfilled merge tags such as {{first_name}}. Use the spam word checker for the message text and the word & character counter for anything else.
Frequently asked questions
Are the phone and Gmail previews exact?
No. They are estimates from typical character limits; the real cut-off changes with screen size, font size and app.
Does subject length affect open rates?
It can, but tests on your own audience matter more than any general rule; try two versions and compare.
Is my text sent anywhere?
No. It stays in your browser.