Email subject line tester
Analyze your email subject line before sending: ideal length, spam filter trigger words, excessive capitalization, emojis and punctuation. 100% local analysis — nothing is sent to a server.
How it works
An email's subject line largely determines its open rate, but also the risk of it being filtered as spam before it even reaches the inbox. This tool locally analyzes your text against several objective criteria: character length, presence of words frequently associated with spam campaigns, excessive use of capital letters or punctuation, and presence of emojis.
Why does the subject line length matter?
Beyond about 60 characters, most email clients (Gmail, Outlook) truncate the subject in the display, especially on mobile where available space is limited. A subject that is too short, conversely, sometimes lacks the context needed to make people want to open the message. A range of 20 to 60 characters is generally recommended.
Does this analysis guarantee my email will avoid spam filters?
No: real anti-spam filters from email providers combine dozens of signals (sender domain reputation, message body content, recipient complaint rate...) that this tool cannot assess. This analysis focuses solely on the objective signals present in the subject text, to flag the riskiest wording before sending.
The entered subject is never sent anywhere: the entire analysis happens locally in your browser.