Cold email subject line checker
Check your subject line before you send it: length, spam-trigger words, tone and personalisation.
Your result
Phone preview
What makes a good cold email subject line?
A good cold email subject line is short, specific to the reader and honest about what is inside. It reads like a note from a person, not an advert. The best ones mention something that matters to the reader: their company, a goal they have or a change you noticed.
What the checker looks at
- Length. Long subject lines get cut off, especially on phones. The checker uses Mailchimp’s guidance: no more than 9 words and 60 characters (checked November 2026).
- Spam-trigger words. Words like “free”, “guaranteed” or “act now” make an email look like a promotion.
- Shouting. Words in capitals and exclamation marks read as pushy.
- Fake replies. “Re:” or “Fwd:” on a first email breaks trust the moment it is opened.
- Broken merge tags. A leftover {first_name} shows the email was sent in bulk.
- Overused openers. “Quick question” and “Just checking in” are easy to ignore.
- Personalisation. Their name or company makes it clear the email is for them.
Subject line examples
| Before | After |
|---|---|
| FREE audit for your business!!! | A few ideas for Acme’s onboarding |
| Re: our call | Sarah, a question about your Q1 hiring |
| Quick question | How Acme handles late invoices |
The subject line gets the email opened; the first lines get the reply. See examples of personal outreach messages for what to write next.
Cold email subject line checker FAQs
Is the subject line checker free?
Yes. Check as many subject lines as you like without signing up.
How long should a cold email subject line be?
No more than 9 words and 60 characters, which is Mailchimp’s guidance. Shorter is clearer on a phone: three to seven words usually say enough.
Should I use the person’s name in the subject line?
It helps when it reads naturally. Their company or a specific goal of theirs often works just as well.
Is my subject line saved?
No. What you type stays on this page and is not saved.