Free Email Subject Line Length Checker
Check your email subject line's length against mobile, Gmail and Outlook cut-off points so it never gets truncated in the inbox — free, instant and private.
Aim for a subject line that stays readable everywhere. Mobile inboxes cut off around 33 characters, most desktop clients around 60.
What is the email subject line length checker?
An email subject line length checker is a free tool that shows whether your subject line will display in full or get cut off across email clients. You type your subject line and it counts the characters live and tells you if it fits on mobile (which truncates around 33 characters), Outlook (around 60) and Gmail on desktop (around 70). Slashit's checker runs in your browser, so nothing is uploaded, and it helps marketers and anyone sending email write subject lines that land the key words before the cut-off — where they actually get read.
How our free email subject line length checker works
Type your subject line
Enter the subject line you're planning to send.
See the live count
The character count and a progress bar update as you type.
Check each inbox
Chips show whether it fits or gets cut off on mobile, Outlook and Gmail desktop.
Who uses our free email subject line length checker?
Email marketers
Make sure the important words land before the mobile cut-off.
Newsletter writers
Write subject lines that display in full across clients.
Sales & outreach teams
Keep cold-email subject lines short and readable on phones.
Why use the email subject line length checker?
Multi-client preview
See mobile, Outlook and Gmail cut-offs at a glance.
Live feedback
The count and status update instantly as you edit.
Free & private
No sign-up, and your subject lines stay in your browser.
Frequently asked questions
What's the ideal subject line length?
Around 30–40 characters is safest so it isn't cut off on mobile, where most email is now opened. Under ~60 keeps it readable on most desktop clients too.
Why do subject lines get cut off?
Each email app shows only so many characters before truncating with an ellipsis. Mobile shows the least, so front-load your key words.
Is it free?
Yes — it's free, needs no sign-up, and runs entirely in your browser.
