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Cold Email Subject Line Tester
Type a subject line and get a score out of 100, what to fix and a preview of how it looks in the inbox.
Send it
- Short. 5 words. Short subject lines look like they came from a person, not a campaign.
- No spam words. No words that look like a promotion.
- Honest. No fake “Re:” or “Fwd:”.
- Calm. No shouting: no all-caps words or stacked punctuation.
- Specific. It has a name, company or number that makes it about them.
- Not generic. No emoji and not a stock phrase.
How the subject line tester works
It runs your subject line through six checks from our cold email checklist and adds up the points: short (two to seven words), no spam words, honest (no fake “Re:” or “Fwd:”), calm (no all caps or stacked punctuation), specific (a name, company or number) and not generic (no emoji or stock phrases). The score is a checklist, not an open-rate prediction.
The one rule that matters most
Never mislead the reader. A subject line that tricks someone into opening starts the relationship with a lie, and the FTC's CAN-SPAM guide bans deceptive subject lines in commercial email. Once they open, the email has to earn the reply. Our follow-up email generator helps with the next one.
Read next
- Follow-up email generator for five sales situations
- Follow up email to sales call: 7 templates that get replies
- Tools for sales prospecting: 8 picks and how to choose
Frequently asked questions
What makes a good cold email subject line?
It looks like a note from a person: short, specific to the reader, honest about what's inside, and free of hype. If it could be sent to anyone, it's too generic.
How long should a cold email subject line be?
Our checklist gives full marks to two to seven words. Short subject lines read like internal email and are less likely to be cut off on a phone. Test longer ones if your data says they work for your market.
Which words should I avoid in a subject line?
Words that sound like a promotion, such as “free”, “guaranteed”, “act now” or “100%”, plus all caps and stacked exclamation points. They read like an ad, and they're common in spam.
Can I put “Re:” on a cold email?
Not on a first email. The FTC's CAN-SPAM rules say subject lines can't be deceptive, and a fake “Re:” pretends you've already talked. Use it only on a real reply.
How is the score calculated?
Six checks, weighted: short (25), no spam words (20), honest (20), calm (15), specific (10) and not generic (10). It's our editorial checklist, not a prediction of your open rate. Your own A/B tests are the final word.
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