Free Marketing tool · runs in your browser
Email Subject Line Builder
Get a set of subject line options for newsletters, promotions, invitations and follow-ups. Pick a purpose and tone, add a keyword, and edit the results.
Your email
Subject line ideas
Your subject line options will appear here.
Rules-based suggestions generated in your browser — not an AI model. Green: up to 50 characters · Amber: 51–70 · Red: over 70.
How this tool works
For each purpose there is a library of proven subject line structures, such as “Introducing [topic]”, “Your [offer] for [topic]” or “Following up on [topic]”. The builder fills them with your keywords, offer and audience, skips patterns that need details you didn’t provide, and adjusts wording for the tone you chose. “More ideas” reshuffles the patterns. Nothing is sent to a server.
Example
Before you send
- Make sure the subject matches the email — misleading subject lines erode trust.
- Read it on a phone; the first few words matter most.
- Pair it with a preview text line that adds information rather than repeating the subject.
- Track clicks with consistent links from the UTM Builder.
Frequently asked questions
Is this an AI subject line generator?
No. It is a rules-based builder: it combines your purpose, audience, tone and keywords with a library of subject line patterns. It runs in your browser, does not call an AI model and does not predict open rates.
How long should an email subject line be?
There is no single right length — what is visible depends on the email app and screen. Shorter subject lines are less likely to be cut off, so the counter flags lines over 50 characters for a second look.
Can I use urgent wording such as “Last chance”?
Only if it is true. Urgency that is not real damages trust and may break advertising or consumer rules in some places. Pick the urgent tone only for genuine deadlines.
How do I know which subject line works best?
Test with your own audience. Most email platforms support A/B testing two subject lines on a sample before sending the winner to everyone.