Cold email subject line generator with a real inbox preview

This generator writes subject lines for cold outreach, not for newsletters. That distinction matters more than you'd think: a line that works on a list of 40,000 subscribers who opted in will get you ignored by a stranger reading on a phone between two meetings.

Fair warning before you scroll. The subject line is the smallest part of the problem, and we'd rather say that now than sell you a magic template.

How to use the subject line generator

Three fields, one dropdown, no account. Here's what to put in each one.

• 📦 What you sell. Write it the way a customer would say it, not the way your website says it. "Recruiting software" beats "talent acquisition orchestration platform" every time.
• 👥 Who you're writing to. The job title, as it appears on their profile. It changes which lines make sense: a founder and a Head of Talent don't open the same emails.
• 🏢 Their company. Optional, and worth filling in. A company name in the subject line reads like an email meant for one person, because it is. Skip it, and you get a merge tag you can paste straight into your sequencer.
• 🔔 Why you're writing now. This is the one that changes everything. A new role, a funding round or an open job gives you a reason to exist in their inbox today.

Hit generate and you get eight lines, each one sitting inside a phone inbox mock so you can watch where your line gets cut off. Take two. Send them to different halves of your list, wait a week, and keep the winner. If you can't answer the "why now" question, that's worth noticing, and we'll come back to it further down.

Each line carries three scores, the ones you'd otherwise eyeball. Length is the number of characters, and green stops before 40. Spam risk counts the words filters were trained on years ago, plus capitals and exclamation marks. Personalization checks one thing, whether the line names their company or the reason you picked today. A line can pass all three and still be the wrong line to send, which is the point of the last section on this page.

What makes a cold email get opened

Start with the uncomfortable number. In the biggest public dataset on outreach, Backlinko and Pitchbox analyzed 12 million outreach emails and found that only 8.5 percent of them got any response at all. The other 91.5 percent went nowhere, and plenty of them were perfectly well written.

The same study found that personalized subject lines lifted response rates by 30.5 percent, which makes it the biggest single lever in the dataset. Personalized here doesn't mean a first name dropped into a template, and it never did. It means the line could not have been sent to anybody else.

One more number before you optimize anything: open rates lie now. Apple's Mail Privacy Protection downloads remote content in the background whether the recipient engages or not, so a large share of your reported opens never happened. Reply rate, dull as it is, is the only number left that tells you the truth.

30 subject lines that work for cold outreach

These are the thirty lines the generator draws from, grouped by the moment you're writing in. Swap the placeholders for your own words. All lowercase is deliberate: a subject line in title case looks like a campaign, and a lowercase one looks like a person typed it in a hurry.

Lines that reference a trigger

The strongest category by far, because they answer the only question the recipient's asking: why you, and why today.

• new role, quick idea
• congrats on the move
• your first 90 days at {company}
• before you hire another {role}
• congrats on the round
• spending the round on {what you sell}?

First touch when you have no context

Harder. These lines admit it instead of hiding it, and the self-deprecating ones outperform the clever ones because they lower the stakes of opening.

• quick question, {role}
• {what you sell} at {company}
• two minutes?
• probably not for you
• {company} + {what you sell}
• bad timing?

Follow-ups that don't say "just following up"

Follow-ups are where most of the replies come from, and the subject line usually gets recycled from the first email. Give it its own line instead. If you want the message underneath as well, our tool for the follow-up itself drafts it by scenario.

• one more thing on {what you sell}
• did this land at the wrong time?
• should I stop here?
• closing the loop on {company}
• quick recap, two lines
• still worth a look?

Re-engagement and breakup emails

The breakup email has a bad reputation, mostly because people write it passive aggressively. Drop the passive aggression and it's often the highest reply-rate email in the whole sequence.

• closing your file
• wrong person?
• last one from me
• parking this until Q3
• should I try someone else on your team?
• no hard feelings

Asking for the meeting

Once there's a conversation, the subject line does a different job. By then it has one job, which is making the calendar step feel small.

• 15 minutes next week?
• Thursday or Friday?
• worth a call, or send it in writing?
• your team + mine, 20 minutes
• happy to just send the numbers
• who else should be on the call?

The 7 rules we apply to every subject line

• 🧮 Six words or fewer. Most phones cut the line off around forty characters, and the cut lands mid-word. Anything after that lands on nobody.
• 🎯 One idea only. A subject line that carries two ideas carries none. Pick the one that would make them curious, and drop the other.
• 📝 Lowercase. Title case signals a campaign. Lowercase signals a person.
• 🔒 No promise you can't keep. If the line says "revenue" and the email says "quick intro", you've taught them to ignore you next time.
• 🔗 It has to match the first line of the body. The preview text is read at the same moment, which is why the generator shows you both together.
• 🧪 Two variants at most. Testing eight lines on a small list gives you noise, dressed up as rigor.
• 💬 Read it out loud. If you wouldn't say it to their face in a corridor, don't put it in an inbox.

What is the 30/30/50 rule for cold emails?

People ask this constantly, so here's the answer. The 30/30/50 rule splits the outcome of a cold email into three parts: 30 percent from the subject line and the opening, 30 percent from the body, and 50 percent from the follow-up. The numbers pass a hundred on purpose, because every follow-up compounds on work the first email already did. No controlled study produced those figures. They're a rule of thumb, one that circulated among sending teams and stuck.

The versions disagree with each other too. Some people swap the first 30 for list quality, which tilts the whole framework toward who you picked instead of what you wrote. Both camps can't be right, and the disagreement is the interesting part. What survives every version is the ceiling: your subject line is worth about a third, and never more. Spend the rest on the body, and more of it on the messages that come after. Our twelve templates that get replies cover both, and this page covers the line at the top.

Subject line mistakes that kill your open rate

Fake "RE:" and "Fwd:" prefixes. They still work on the open, which is exactly the problem. The recipient realizes within a second that you lied to get in, and that's the last thought they have about your company.

Full caps and multiple exclamation marks. Filters have been reading those two signals for twenty years, and they read yours in milliseconds. You're not being bold, you're being classified. The scorer on this page flags both.

The name-only line. "John" or "John, quick question" was clever in 2018. Everybody does it now, and it reads as automation instead of attention.

Emojis in B2B cold email. Test them if you like, but they don't render the same way across clients and they can tip a borderline email into the promotions tab.

A line written for the sender. "Introducing Acme, the leading platform for..." is a line about you. Nobody opens an email about a stranger's company. If your opening sentence has the same problem, our opener tool builds it from something the person did instead.

Who this generator is for

If you send fifty thousand emails a month, this tool isn't for you and neither is the advice around it. Everything here is calibrated for small teams, sending a few hundred emails to people they picked one by one. Once the line works, the body of the email and the pitch it leads to have their own free tools here.