Our free Subject Line Researcher tool tests different keywords to help you write an effective subject line. Below, we walk through how to use this tool in the Campaign Builder, as well as provide other tips for writing subject lines that lead to higher open rates.

In this article:

Using the Subject Line Researcher

  1. Navigate to the Setup step of the Campaign Builder.
  2. Click the How do I write a good subject line? link under the Email subject field.
    Subject line researcher link
  3. In the How do I write a good subject line? pop-up modal, click the option for Subject line researcher.
    Subject line researcher
  4. Type some terms into the Subject line terms field on the Subject Line Researcher window and press the Search button to populate results. For the best results, enter one term or phrase per line and use no more than 3 terms per phrase. Keeping the search broad will allow you to see subject lines that incorporate those terms in different ways than expected.
    Search for subject lines using key terms

    MailChimp will compare those terms to all subject lines ever used in our system, displaying a 5-star rating system for how the subject lines containing those terms performed.

    Subject line researcher results

    In addition to the Subject Line Research tool, consider creating an A/B Split campaign to experiment with two subject lines on the same campaign.

Tips for writing subject lines

  • The best subject lines are straightforward
    Sounds simple, but subject lines should describe the subject of your email. When it comes to email marketing, the best subject lines tell what's inside, and the worst subject lines sell what's inside.
  • Don't confuse newsletters with promotions 
    If your email is a newsletter, put the name and issue of the newsletter in your subject line, because that's what's inside. If your email is a special promotion, tell your subscribers what's inside. Either way, don't write your subject lines like advertisements.
  • Always set your subscribers' expectations during the opt-in process about what kinds of emails they'll be receiving
    If subscribers signed up to receive updates on your company, don’t send an email with a subject line like, “10% Discount! Open Now!” On the other hand, if your subscribers specifically opted in to receive discounts and promotions, there’s nothing wrong with saying there’s a coupon inside.
  • Use groups and segments for your list
    Collecting subscriber data to use with groups and segments helps target subscribers who are most interested in what you have to say. If your subscriber data indicates that someone is interested in vegetarian recipes, then they probably won’t open an email with a subject line about the 10 best meat recipes. If subscribers provide information to help target your message to them, then use it. Otherwise, you’re cluttering their inbox with emails they don’t want and likely won’t open.

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