Cold email subject line tester
Type a subject line to see roughly where a phone and a desktop inbox cut it off, plus plain notes on anything that makes it read like an ad.
Length and preview
- Characters
- 0
- Words
- 0
These cut-off points are typical, not exact. Every mail app, screen size and font setting shows a different amount.
Things to look at
These are suggestions, not a score. No tool can tell you from the subject line alone where an email will land.
This tool runs entirely in your browser. Nothing you type is sent to or stored by Next Reply. The notes are advice, not a deliverability score.
How the subject line is checked
Every check is a simple rule you could apply by eye. There is no hidden score.
- LengthCharacters and words are counted after extra spaces are removed.
- Inbox previewThe phone row cuts the line at about 35 characters and the desktop row at about 60. These are typical cut-off points, not exact ones.
- ShoutingFlags a line written in all capitals, single words in capitals, any exclamation mark, and more than one question mark.
- Emoji and fake repliesFlags emoji, and RE: or FW: at the start, which implies a conversation that has not happened on a first email.
- Salesy wordsCompares the line with the same list of promotional terms the spam word checker uses.
- Too long or too shortFlags lines likely to be cut off, and one-word lines that may be too vague.
Subject lines that read like a person sent them
Lead with the reader's situation
The strongest cold subject lines name something the reader already deals with, in the words they would use for it. A plant manager thinks about overtime on second shift, not about workforce optimization. Find the plain phrase your buyers use for the problem and put it first.
Write it the way you would write to a colleague
Use sentence case, no exclamation marks, and no brackets or emoji. Three to six words is a good range. A subject line that looks like a newsletter gets treated like one, so it should look like it came from one person to another.
Make the email keep the promise
The first line of the email should pick up exactly where the subject line left off. A subject that hints at something the email never delivers may get opened, but it gets ignored or reported after that, and that hurts the next send.
Judge subject lines by replies
Open rates are unreliable because mail apps load or block tracking images on their own. To compare two subject lines, send each to a few hundred similar prospects with the same email body and compare replies. A small difference on a small list is usually noise.
FAQ
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One that looks like it came from a person, not a campaign. Keep it short, specific to the reader, and written in normal sentence case. It should describe the email honestly, because a subject line that tricks someone into opening rarely leads to a reply.
Short enough that the important words show on a phone. Phones often show roughly the first 35 characters and desktop inboxes roughly the first 60, but it varies with the mail app, the screen and the font size. Put the words that matter first.
A score would be made up. No tool can tell from a subject line alone whether an email reaches the inbox or gets a reply. That depends on your list, your sender reputation and whether the email is relevant. The notes here point out things worth a second look.
No. On a first email it suggests a conversation that never happened. Some people will open it, but they notice the trick, and it is a poor way to start a business relationship.
Yes. A marketing email goes to subscribers who expect offers, so promotional wording is normal there. A sales email goes to one person who has not heard of you, so the subject line works best when it reads like a note from a colleague.
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