As with most tools, email subject line tools are just that. They are tool to help you make a decision, not tool to make a definitive decision for you. These tools use algorithms to give a score and just because you get a good score based on that algorithm doesn’t mean that it makes sense to use.
But these tools can help choose or improve already good email subject lines.
Come up with lots of ideas for a subject line. Then narrow it down to a few that you love, use these tools to find the best fit and perhaps hone the title just a bit.
Please note that pricing and access information may change without notice and is current as of writing.
Subject Line (Worldata)
Free (requires detailed sign up after the first evaluation)
I tested a few subject lines.
- “A funny thing happened on the way to the forum” got a score of 81 with points being taken for a lack of subtle urgency. Adding a period at the end brought the score to 85. And “A funny thing happened on the way to the forum today.” got a score of 97.
- “A funny thing happened . . .” got a score of 85 with points removed from a lack of subtle urgency (-19 pts), and points being added for containing punctuation (+4 pts).
- “A funny cyclops lopped . . .” got a score of 85 with exactly the same points.
The Omnisend Email Subject Line Tester (Omnisend)
Free Email Subject Line Tester | Boost Open Rates | Omnisend
Free (no sign in required)
This tester gives an overall score and then goes on to analyze the length (characters and words), wording (helpful words and negative words), scannability, as well as giving subject line previews.
Changing case with this tool did create a colour change on the “Capitalization Style” section of the report, but did not change the score.
Test subject lines.
- “A funny thing happened on the way to the forum” got a score of 58%.
- “A funny thing happened . . .” got a score of 75%
- “A funny cyclops lopped . . .” also got a score of 75%
Email Subject Line Grader (Net Atlantic)
Free (no sign-in required)
This tool gives an overall score and more.
It gives you suggestions on how to improve your email subject line, rates your character and word counts, word mixture and balance.
Test subject lines.
- “A funny thing happened on the way to the forum” got a score of 70.
- “A funny thing happened . . .” got a score of 100 (whoo hoo?).
- “A funny cyclops lopped . . .” also got a score of 100.
I personally prefer the second subject line and that is the one I used. I am not sure it deserves a score of 100 and as you can see the third option made no sense and still got a perfect score.
Email Subject Line Analyzer (Attrock)
The Email Subject Line Analyzer You Need | Attrock
Free. (requires free account with name and email, but I never got my report and get asked for the same information every time I come back to the tool)
This tool gives you an overall score and then goes on to evaluate “good” words, “bad” words, word and character count, case (apparently title case gets more opens), subject line type, emoji count and personalization.
It goes on to show how your subject line will look in various inboxes.
The tool also provides a “Good Words Bank” and a “Bad Words Bank”. From what I have read, “Good Words” reportedly increase the chances of your email ending up in spam. For example “freebie”, “buy”, “save.”
Test subject lines.
- “A funny thing happened on the way to the forum” got a score of 27.
- “A funny thing happened . . .” got a score of 51.
- “A funny cyclops lopped . . .” also got a score of 46.
I played with subject line 2 and eventually managed to get a score of 96 with this silly and unsendable subject line: “A Really Funny 🤣 Thing Happened, Jane?”
Email Subject Line Tester (CoSchedule)
Email Subject Line Tester from CoSchedule
Free (requires sign up)
In addition to an overall score, this tool highlights and talks about words that increase and decrease opens. The also cover case, character, word and emoji counts, the presence or absence of numbers. It also gives a preview of the subject line in 3 formats.
With this tool, capitalization does affect the score, by up to 7% from my testing.
Other Fun Things to Try
When you get an email with a subject line that you think is really good or really bad, pop it into one of these subject line analyzers and see if you can roughly guess the score it will get. Then you can play with those headlines to improve them to practice your headline skills.
For example, I got an email with the subject line “Do you use this secret ingredient in your marketing?” It got a score of 71%
I tweaked it to “Do you use this secret to promote?” and got 100%.
Personally, I think that regardless of what score I got, I think the first subject line is the stronger of the two.
With the Omnisend Tester the first subject line got 42% and the second got 83%.
How Did This Blog Post Title Do?
While this is a blog post, not an email subject line, I thought it might be fun to see how it did with some of the analyzers. And if it does well and you are part of my community, you might see an email with this subject line coming your way.
Subject line: “5 Free Tools to Help You Write Better Email Subject Lines.”
Subject Line: 88%
Omnisend: 83%
Email Subject Grader: 75%
Email Subject Analyser: 44%
Email Subject Line Tester (CoSchedule): 56%
See the chart below for scores for a variation.
Conclusion
As with all such tools, these subject line analyzers can help guide you, but common sense and intuition always beats the recommendation of a tool. As you can see with my third example, this nonsensical title scores almost as high and the concise and intriguing title “A funny thing happened. . . “
Each tool gives completely different scores based on different criteria.
For best results, choose a few subject lines that make sense and that you love, then put those into the analysis tools to narrow your search and tweak in a thoughtful way.
| Subject Line (Worldata) | The Omnisend Email Subject Line Tester | Email Subject Line Grader (Net Atlantic) | Email Subject Line Analyzer (Attrock) | Email Subject Line Tester (CoSchedule) | |
| A funny thing happened on the way to the forum | 81 | 58 | 70 | 27 | 44 |
| A funny thing happened . . . | 85 | 75 | 100 | 51 | 44 |
| A funny cyclops lopped . . . | 85 | 75 | 100 | 46 | 44 |
| Free tools to help you write better email subject lines | 98 | 75 | 75 | 47 | 51 |
| 5 free tools to help you write better email subject lines | 88 | 83 | 75 | 44 | 56 |
