Free tool
Email subject line checker
Type the sender name, subject and preview text of your next campaign. Eight checks run as you type, and the phone preview shows how much of it a reader will see.
Pre-flight check
Type an inbox line, or start from a draft.
How it lands on a phone
now
Lift What gets it opened
Subject length
First words
Preview text
Sender name
Drag What gets it ignored or reported
Capitals
Punctuation and emoji
Spam-sounding phrases
Honest framing
Nothing leaves this page: what you type stays in your browser. These are rules of thumb for the inbox line, not a deliverability test. The sample senders are invented.
About the checker
Is the subject line checker free?
Yes. It is free, needs no account and has no limit on how many subject lines you check.
What does it check?
Eight things across the sender name, subject line and preview text: length, the first words, preview text, sender name, capitals, punctuation and emoji, spam-sounding phrases and misleading "Re:" or "Fw:" prefixes.
Where does my text go?
Nowhere. The checks run in the page on your own device. Nothing you type is sent to a server or stored, and it is gone when you close or reload the tab.
How long should an email subject line be?
There is no exact limit, because every mail app shows a different amount. Many phone inboxes show roughly 35 to 45 characters, so the checker passes up to 50 and asks you to put the point in the first 40.
Will a passing result keep my email out of spam?
No tool that reads only the text can promise that. Spam filtering depends mostly on your sending domain, authentication, list quality and how readers react. The checker removes the avoidable mistakes in the inbox line.