Free tool
Cold email subject line tester
Paste a subject line and get an instant score with specific fixes: length, spam triggers, capitalisation, punctuation, and personalisation. Free, and it never leaves your browser.
What the tester checks
- Length: 28 to 60 characters reads well across inboxes, including mobile previews.
- Spam triggers: words like free, guarantee, and act now can hurt deliverability.
- Capitalisation: ALL-CAPS words read as shouting and can trip filters.
- Personalisation: a merge variable such as {{first_name}} or {{company_name}} lifts opens.
Cold email subject lines that get opened
Nobody reads an email they do not open, and the subject line does most of that work. Its job is not to be clever. It is to look like a real message from a real person about something relevant, not like a marketing blast.
What gets opened
- Short and lowercase, the way a colleague would write: 'quick question', 'idea for [company]'.
- Specific to them: a team, a market, a role, or a recent change.
- Curiosity without clickbait: hint at the point, do not oversell it.
- No hype words, no exclamation marks, no 'FREE', no all-caps.
What gets deleted
- Anything that reads like a newsletter subject or an ad.
- Long subject lines that are cut off on mobile before the point lands.
- Fake personalisation that is obviously a mail merge, like 'Re: our conversation' when there was none.
- Promises you cannot back up in the first sentence of the email.
Subject lines to adapt
- idea for [company]'s [team] outreach
- [their market] expansion?
- quick question, [first name]
- worth a look for [company]?
If a subject line could appear in a brochure, rewrite it. It should read like a one-line note from a busy person. Then test it: on Scout and above, HuntSales runs A/B variants on a sequence step and lets you declare the winner once there is enough volume to call it, so the data picks the subject line instead of a guess.
Frequently asked
What makes a good cold email subject line?
Keep it short (roughly 28 to 60 characters), specific, and personal. Use a merge variable like the company name, avoid spam-trigger words and ALL CAPS, and skip heavy punctuation or emoji for B2B.
Is this subject line tester free?
Yes, completely free and it runs entirely in your browser. Nothing you type is sent anywhere.
What is the best subject line for a cold email?
The one your audience opens. The patterns on this page raise the odds, but the honest way to find a winner is to test two variants on real sends and keep the one that gets more opens and replies.
Write subjects that get opened, then send them
HuntSales fills your merge variables per contact and sends from your own mailbox. Start free, and add a warmup ramp on any paid plan.
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