Email Subject Line Tester

Test the performances of your email's subject and get AI-powered suggestions.


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Your subject line

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Alternatives suggested by AI

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Alternatives from GPT-3

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The fastest way to verify an email subject line

Email Subject Line Tester by Mailmeteor scores an email subject line in a few seconds for free, and generate alternative subject lines powered by AI. Checks are made at multiple levels: length, number of words, number of question mark and exclamation points, presence of emojis or spam words. Make sure your emails reasonate with your audience.

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How it works

Learn why and how to test your email subject lines with our 2-min video tutorial.

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Questions & answers about email subject line tester

Everything you need to know about how and why checking email subject lines.

Email subject line tester is a free, easy to use and simple tool. Just enter the email subject line and click on "Test". We will then proceed with a test providing you alternative subject lines and scoring all of them so you can you choose the best option for your email.

Email subject line tester is a free tool to test anyone's email subject line. It tests that the email subject line is well conceived, with the good length and without too much spam related wording. In case we detect something wrong, the email subject line score will decrease.

Email subject line tester proceeds with several checks to determine if an email subject line is valid:

  1. The email subject must be well formed, not too short and not too long.
  2. It should be grammatically correct, with first letter as a cap and ponctuation.
  3. The email subject can include emoji but they should not be too numerous.
  4. The subject line should not contain spam words.

Depending on the provided email subject line, we might apply extra-checks on a per basis.

Your subject line is submitted to an AI (OpenAI GPT-3) that will suggest improvements. AI is not perfect (yet) and might suggest inacurrate responses. Please let us know of any inappropriate suggestions.

Email Subject Line Tester is totally free to use. Mailmeteor makes it available to anyone interested in checking an email subject line and make sure you will be read.

We apply a fair-use policy, so you are free to manually use Email Subject Line Tester as long as you don't abuse of it. Any abuse includes, but is not limited to, making automatic requests to our service.

Your data stays yours - like all products made by Mailmeteor. Email addresses that you verify using our email subject line tester are not saved by us nor shared with a third-party. Although, we might temporarly log requests made to the service for maintenance purposes.

With this said, this page has Google Analytics and is protected by reCAPTCHA. Consequently, the Google Privacy Policy and Terms of Service apply.

Once you have verified your email subject line and found the most efficient, you can send a highly personalized email campaign using Gmail with Mailmeteor. Mailmeteor lets you send mass emails in Gmail that feel personal. It’s the most popular Gmail mail merge tool, Trusted by 5 million people worldwide for its simplicity and privacy focus.

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