Email Subject Line Checker
See how your subject line looks in an inbox and catch the things that make emails look like spam.
Approximate inbox preview
PhoneAlex from Northwind · Quick question about your onboardin…
DesktopAlex from Northwind · Quick question about your onboarding process
- ✓ 44 characters: short enough to read in full on most screens.
- ✓ No common red flags found.
Subject lines that get opened
- Be specific. "Question about your Melbourne store" beats "Quick question".
- Lead with the reason. The first few words are often all a phone shows.
- Sound like a person. Lower case, no hype, no fake urgency.
- Match the email. A subject that over-promises hurts replies and trust.
Frequently asked questions
How long should an email subject line be?
Short enough that the key words are visible: many phones show roughly the first 30–40 characters in the inbox, and desktop inboxes around 60. Put the important words first.
Is this a deliverability score?
No. It checks well-known rules of thumb (length, capitals, spam words, misleading prefixes). Whether an email reaches the inbox depends far more on your sending domain, authentication and recipients' engagement.
Are emoji good in subject lines?
One can help in friendly marketing emails. In cold or formal outreach they usually look promotional, so leave them out.
Is my subject line sent anywhere?
No. The check runs in your browser.
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