Top 15 Email Subject Line Testers Compared (Features + Rating)

If you're looking for ways to improve your email marketing campaigns, one of the most important factors to consider is the subject line. The subject line is the first thing that your recipients see, and it can make or break their decision to open your email or ignore it.

But how do you know if your subject line is catchy, clear, and compelling enough to entice your audience? That's where email subject line testers come in handy. These are tools that help you analyze and optimize your subject lines based on various criteria, such as length, sentiment, emotion, keywords, spam score, and more.

Here, we have covered 15 email subject line testers and how they can help you optimize your subject lines for better campaign performance.

Subject line testers are online tools usually offered by ESPs and email marketing platforms to help you optimize your email subject lines for higher open rates, click-through rates, and conversions.

They analyze your subject lines based on various criteria, such as length, word choice, sentiment, personalization, punctuation, and spam triggers. They also provide you with feedback, suggestions, and best practices to improve your subject lines and make them more appealing to your audience.

Email subject line testing can help you optimize your email marketing campaigns and achieve your goals more effectively. By testing different subject lines, you can learn what works best for your audience and your business, and optimize your email performance accordingly.

Some of the benefits of email subject line testing are:

Now that we know why a subject line tester is important. Let’s jump onto the most efficient tools used for email subject line testing…

Omnisend offers one of the best free subject line testers. It helps you create engaging email subject lines while avoiding spam filters, locking in better chances of getting into your recipient’s notice.

Top features of Omnisend email subject line tester:

Moosend's Refine is a free email subject line testing tool that assists marketers and businesses in increasing open rates and maintaining a consistent deliverability score.. It analyzes your subject line based on various criteria, such as length, word choice, sentiment, and punctuation, and gives you a score and feedback on how to improve it.

Top features of Refine subject line tester:

⭐ G2 Crowd rating: 4.7/5

CoSchedule headline analyzer is another popular tool that helps you write better headlines and subject lines. It scores your subject line based on four factors: word balance, headline type, length, and sentiment. It uses a variety of graphics to gradeyour email subject lines and suggests ways to improve them.

Top features of CoSchedule email subject line tester:

⭐ G2 Crowd rating: 4.4/5

Grademyemail is another AI-powered subject line tester tool that helps you write effective email subject lines to get more opens and replies. It analyzes your subject line based on best practices and gives you a score and feedback on how to improve it.

Top features of Grademyemail subject line tester:

⭐ G2 Crowd rating: 4.4/5

SubjectLine.com is one of the most popular and widely used subject line testers for anyone who wants an easy way to check subject lines for common pitfalls and best practices. It evaluates your subject line based on over 800 unique rules that are proven to increase open rates. It gives you a score out of 100, along with suggestions on how to improve your subject line.

Top features SubjectLine email subject line tester:

⭐ G2 Crowd rating: N/A

Mailmeteor is another quick and free email subject line tester that helps you with email subject line scoring and various subject line templates even without signing up. What’s unique about Mailmeteor is its integration with ChatGPT which makes crafting new and relevant subject lines much easier.

Top features of Mailmeteor subject line tester:

⭐ G2 Crowd rating: 2.3/5

Email Subject Line Grader is a simple email subject line testing tool that grades your subject line based on various criteria. It scores your subject lines out of 5 stars, along with feedback on how to improve your subject line. The tool is especially useful for intermediate users who want to polish their writing and styling skills.

Top features of Email Subject Line Grader:

⭐ G2 Crowd rating: N/A

Send Check It is a comprehensive email subject line tester for anyone who wants a detailed and thorough analysis of their subject line. The tool analyzes your subject line based on 15 different metrics, and gives you a score of 100%, along with suggestions on how to improve
your subject line.

Top features of Send Check It subject line tester:

⭐ G2 Crowd rating: 3.2/5

EmailTooltester’s Free Subject Line Tester is a simple testing tool that shows you how your subject line will look on different mobile devices, such as the iPhone, iPad, Google Pixel and Samsung smartphones. It also previews what your sender name and preheader text will look like, so you can optimize them for better visibility and engagement.

Top features of Free Subject Line Tester:

⭐ G2 Crowd rating: N/A

Subject line helper is a comprehensive email subject line testing tool that comes free with your Mailchimp account. It helps you boost your email campaign performance by providing instant feedback on the quality of your email subject line. While covering most of what other subject line testers provide, the tool still fails to evaluate your subject line based on sentiments, reading level, and scanability.

Top features of Subject Line Helper:

⭐ G2 Crowd rating: 4.4/5

This email subject line testing tool by MailNinja is another tool that provides in-depth analysis on what has to be changed for your subject line to produce great results. You need to provide your contact details to get the suggestions. The change suggestions provided can help you increasing your email open rates and maintaining an edge over the competition.

Top features of free email subject line tester by MailNinja:

⭐ G2 Crowd rating: 4.0/5

Mizy is a smart and easy-to-use free subject line testing tool that works with AI and deep learning algorithms to help you craft the best subject line. The tool looks up a database of emails along with their open and click-through rates. It’s capable of collecting relevant data and restructuring itself to give more insights into what can work to generate better email campaign results.

Top features of Mizy email subject line tester:

⭐ G2 Crowd rating: 2.1/5

Spam Check By Postmark is a tool that helps with subject line testing to ensure your emails are not mystified as spam. It is a free API that helps you score the quality of your outbound (and inbound) emails. It provides easy and fast programmatic usage of the spam filter tool SpamAssassin to evaluate the spam score of your subject line and email messages.

Top features of Spam Check subject line tester:

⭐ G2 Crowd rating: 4.8/5

Lavender is an AI sales email coach tool that helps thousands of sellers around the world craft better emails faster, getting them more positive replies in less time. It also provides a strong email subject line tester that helps you achieve a better open rate.

Top features of Lavender email subject line tester:

⭐ G2 Crowd rating: 4.9/5

Email Copy Analyzer by Mailshake is an intuitive tool that analyzes your email copy and provides feedback on how to improve. Mailshake also offers A/B testing, automation, and drip campaigns to help you ace all your campaigns The top two features of Email Copy Analyzer by Mailshake are:

Top features of Email copy analyzer :

⭐ G2 Crowd rating: 4.7/5

Not all tools are created equally. While some provide greater insights, some are backed up by real data and expert knowledge, and some provide top-notch AI assistance.

Therefore, it's best to first try a few tools, gain a thorough grasp of your email campaign performance, as well as where you need assistance, before selecting the tool that best suits your needs.

You can tests for character length, spam filter resistance, emotional marketing value, and other factors are that might impact your campaigns. Even better, consider combining these techniques to find the sweet spot where innovation meets technology and analytics to increase email open rates.