Email subject line generator: options that say what is inside.
Describe what the email is about, such as a price change, a new guide or an event. The tool returns several subject line options. Pick one, edit it, and test it on your own list.
By Mike Cecconello · Updated September 25, 2026
Email subject line generator
Runs on our server. Your text is sent to Anthropic's Claude to write the result. We count runs and never save what you enter; an identical request may be answered from memory for up to five minutes.
What you can do with it
- Get a few alternatives when your first subject line feels flat
- Draft two options for an A/B test on your own list
- Write a clear subject line for a sensitive announcement, like a price change
- Find a shorter way to say what a newsletter issue contains
How it works, step by step
- 1
Write down the one thing the email is for
Before you write a subject line, finish this sentence: after reading, the recipient should know or do... If you cannot finish it, the subject line will be vague too.
- 2
Say what is inside
The most reliable subject lines tell the reader what they will get if they open. Name the content or the change plainly. Curiosity works sometimes; clarity works more often and never feels like a trick.
- 3
Write the preview text as a pair
Most inboxes show a line of preview text after the subject. Write it on purpose to add the next detail, instead of letting it default to a header or a view-in-browser link.
- 4
Check it on a phone
Send yourself a test and look at it in a mobile inbox. Long subject lines get cut off, so put the words that matter first.
- 5
Test with your own list
If your email tool supports it, send two versions to a small share of your list and send the winner to the rest. Your audience's behavior is the only benchmark that applies to you.
A subject line is a promise
The subject line is how someone decides whether to open an email, and the email is how they decide whether to trust the next subject line. A line that overpromises can win one open and lose the reader’s attention for months. A line that says plainly what is inside tends to earn opens from the people who want it, and that is the audience that matters.
So the first job is not to be clever. It is to be accurate and specific: “Our prices change on 1 May: what it means for you” beats “Big news inside” because the reader can decide in a second.
Write the subject and preview together
Most email apps show a line of preview text next to or below the subject. If you do not set it, the inbox fills it with whatever comes first in the email, often “View in browser” or an image alt text. Treat subject and preview as one unit: the subject names the topic, the preview adds the most useful next detail. Most email tools have a field for preview text, sometimes called preheader.
What to avoid
- Fake replies and forwards. Starting with “Re:” or “Fwd:” when the email is neither is misleading, and deceptive subject lines are prohibited in commercial email under the US CAN-SPAM Act.
- Hype. All caps, strings of exclamation marks and urgency that is not real read as spam to people, even when a filter lets them through.
- Bait and switch. If the subject promises a guide, the email should contain the guide, not a sales pitch with a link to it three screens down.
- Mystery for its own sake. Curiosity can work, but only when the reader already trusts you enough to open without knowing why.
Test on your own list
Published open-rate advice is generic by definition. Your list, your sender name and your sending history are specific. If your email tool supports split tests, send two subject lines to a small share of the list, wait, and send the better one to the rest. Change one thing at a time so you learn what made the difference. Keep a note of what won, and after a few sends you will have a benchmark that applies to you.
The options this tool writes are drafts for that process. Edit them into your voice before you send. For the email body’s call to action, the CTA generator works the same way, and the headline generator helps when the email links to a new article.
AltoRank drafts the articles those emails often point to, planned from a site’s own data, and a person approves each piece before it publishes.
Frequently asked questions
Which subject line will get the most opens?
The tool cannot know. It has no data on your list, your sender reputation or your past results, so it does not score or predict open rates. Choose the option that most clearly describes the email, then test on your own audience if you can.
Should I avoid certain words to stay out of spam?
Deliverability depends mostly on your sending reputation, authentication and whether recipients engage, not on single words. Still, heavy hype, all caps and piles of exclamation marks look like spam to people, which hurts engagement. Plain and specific is the safer default.
Is it fine to start a subject line with Re: or Fwd:?
Not if the email is not actually a reply or a forward. It misleads the reader, and in the US the CAN-SPAM Act prohibits deceptive subject lines in commercial email. It also costs trust the moment someone notices.
How long should a subject line be?
There is no single right length, and inboxes cut off subject lines at different points depending on the device and app. Put the most important words at the start so the line still makes sense if the end is cut.
What happens to what I enter?
Your description goes to our server and on to Anthropic's Claude, a fast model, which writes the options. We count how many times the tool runs and never save what you enter; an identical request may be answered from memory for up to five minutes. There is a daily usage limit so the tool can stay free without a signup.
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