Cold email subject line generator
Get twelve subject lines grouped by angle, written for the person you're emailing. Then check any line in the tester below: how much a phone inbox actually shows, and whether it reads like spam.
Subject line tester: what the inbox really shows
Inboxes cut subject lines to fit the screen. On a typical phone in portrait you get somewhere around 30–40 characters; on desktop, roughly 60–70 depending on window width and the sender name. Type a line and switch devices to see where yours breaks.
- Fix: 42 characters
The end may be cut off on phones — put the words that matter first. - Good: 6 words
Two to seven words reads as a note, not an ad. - Good: No trigger words
Words like free, guaranteed or urgent read as promotional. - Good: No shouting
ALL CAPS and exclamation marks look like marketing. - Good: Honest prefix
Fake replies are deceptive and break trust on open.
Cut off on phone: enewals
What makes a cold email subject line work
A subject line has one job: get the email opened by the right person without over-promising. The email then has to deliver on it. That rules out clickbait — a curious open followed by a pitch feels like a trick and ends in the bin.
- Specific beats clever. "Northwind's second clinic" says you did your homework; "Quick question" says nothing.
- Front-load. Put the prospect-relevant word first, because the end may be cut off.
- Sound internal. Short, plain, often lowercase — like a colleague's email, not a newsletter.
- Stay honest. No fake "Re:", no false urgency. The US CAN-SPAM Act specifically bans misleading subject lines.
Need the email to go with it? The cold email generator writes a matching subject for every variation.
Questions people ask
How long should a cold email subject line be?
Short. Phone inboxes usually show only the first 30–40 characters of a subject, and much of cold email is read on phones. Two to six words, under about 45 characters, keeps the whole line visible.
Should cold email subject lines be lowercase?
Many sales teams use sentence case or all-lowercase because it looks like a message from a colleague rather than a campaign. It is a style choice, not a rule — what matters more is that the subject is specific and honest.
Is it OK to use "Re:" or "Fwd:" on a cold email?
No. Faking a reply or forward misleads the reader, damages trust the moment they open it, and in the US the CAN-SPAM Act prohibits deceptive subject lines.
What are the best subject lines for cold emails?
The ones that match the email. A subject that references the prospect's company, a trigger event or a peer company tends to outperform generic curiosity, because the open is followed by an email that delivers on it.