10 Easy Subject Line Tester Tools to Boost Email Opens


Subject Line Tester Tools

  1. Test Subject

  2. Email Subject Line Grader

  3. Spam Check

  4. Touchstone

  5. SubjectLine.com

  6. ISnotSPAM

  7. Headline Analyzer (CoSchedule)

  8. Hemingway App

  9. Emotional Marketing Value Headline Analyzer 


Do you struggle to get prospects to open your emails? Is writing witty subject lines a little outside your comfort zone? Wish you had a magic tool to help you write better, more eye-catching subject lines, faster? Well, the good news is that such a tool exists. The better news is there are about 10 of them, and I’ve rounded them up below.


Check for spam triggers, get suggestions for making your subject lines more emotive, and get an overall grade on how clickable your emails are. It’s easy to get started. Just pick your favorite few below, plug in your subject line, and you’re off!


Subject Line Testing Tools


1. Test Subject by Zurb
  • What it tests: Appearance on mobile

  • Price: Free


Want to know how your sender name, subject line, and pre-header text will appear on the most popular mobile devices of the moment? This tool gives you an instant preview of how copy will appear to your audience. You know, for those moments you want to avoid someone’s iPhone 6 turning “Products for foolproof marketing” into “Products for fool …”.


2. Email Subject Line Grader by Net Atlantic
  • What it tests: Overall effectiveness of copy, word count, word mixture and balance, and type

  • Price: Free


Receive an overall numerical score on how compelling your subject line is, along with suggestions on how to improve it. You’ll also learn how close your character and word count are to the ideal length (50-65 characters or six-to-seven words).


And, find out how your word mixture and balance measures up. Need a little more emotion, action, or power? Subject Line Grader gives it to you straight.


3. Spam Check by Postmark
  • What it tests: Overall spam score

  • Price: Free


You spend time crafting your emails, and you don’t want them to get caught in someone’s spam folder, right? Copy and paste your subject line, pre-header text, email message, and sign-off into this tool, and find out exactly what will trigger spam filters and trap your emails in “The Upside Down.”


4. Touchstone
  • What it tests: Subject line effectiveness, segment testing, full reporting dashboards, access to Touchstone’s database

  • Price: Essential, $69; Expert, $99; Enterprise, $297


This is a deluxe tool that’s probably best for whole teams rather than individuals. Depending on your tier, you’ll receive subject line testing functionality, email reporting, segment testing, filter options, and technical support.


You can also compare your results with those of the 21 billion emails stored in Touchstone’s database.


5. SubjectLine.com
  • What it tests: Overall copy effectiveness

  • Price: Free


This tool doesn’t beat around the bush. Get an overall score for your subject line, see where and why you lost points (i.e., “Does not contain a sense of urgency” -15 points), and advice for how to make it better.


6. ISnotSPAM
  • What it tests: Spam phrases, sender-ID check

  • Price: Free


Send your email to the address provided in their homepage and receive a comprehensive spam report in return. This tool flags wording or phrases in your subject line and email body that will trip spam filters. It also checks that your own ID is clean, and suggests fixes for any spam-related issues that arise.


7. Headline Analyzer by CoSchedule
  • What it tests: Overall copy effectiveness, word balance, length analysis, keywords, type, and sentiment

  • Price: Free


This tool was built to analyze blog/article headlines, but it works just as well for subject lines. Headline Analyzer gives you an overall headline score and provides tips on structure, grammar, and word placement.


Widely considered the gold standard in headline testers, this is definitely a tool to keep in your back pocket.


8. Hemingway App
  • What it tests: Readability of copy

  • Price: Free


Not a literature buff? Legendary author Ernest Hemingway was known for his straightforward writing style. There were no warm sunset walks festooned with bright spring blooms in his books. Hemingway would have written, “We took a walk. It was warm. The flowers were in bloom.


This app is helpful for editing the body of your email. Copy and paste your follow-up email into this tool to get an overall readability grade, find out where you’ve used passive voice, if you have too many adverbs, and which sentences are hard to read.


9. Emotional Marketing Value Headline Analyzer by The Advanced Marketing Institute
  • What it tests: Emotional Marketing Value (EMV) words

  • Price: Free


Did you know 20% of the English language is made up of EMV words? Find out if your headline appeals to the intellectual or empathetic side of your prospect’s brain, and learn which side you want to appeal to given the goals and content of your emails.


10. Email Subject Line Keyword Checker by Adestra
  • What it tests: Open rate and click rate of subject line keywords

  • Price: Free


This tool asks you to select a business sector and type in your keyword — the main point of your subject line. For example, if my email subject line is, “Checking on contract status” I would type in “Contract” as my keyword.


In this case, the tool would tell me open rates are .35% below average for emails using the word “contract” in the subject line. Given this information, I might choose a different subject line keyword.


Subject lines are the most important part of your email. In fact, 33% of email recipients report opening emails based on the subject line alone. Make the most of inbox attention, and ensure subject lines grab your prospect’s eye every time.