Iuliia Nesterenko

Technical Writer

15 Email Subject Line Generators to Boost Your Open Rate

A subject line is an important element of every email campaign. Together with a sender name, it’s the first thing recipients see in the Inbox. When composed badly, it can also be the last one, so marketers put much effort into cathсy phrases and attention-grabbing expressions.

However, sometimes even the most talented and experienced copywriters get stuck with composing a good email subject line. This is where a random subject generator can help you come up with a couple of smart lines or at least give some inspiration. Most of them are free and easy to use. Just enter the word and choose between the suggested combinations.

Here is the list of 15 free email subject line generators you can start with straight away. Create cool lines that will get your subscribers to pay more attention to your messages.

1. Portent

Type the subject and swipe through the options. Click any word in the title to see why it has been used. Save your ideas or tweet those you find interesting or funny.

Portent subject generator

2. Best Online Title Generator

The most modest subject generator of them all. Enter the keyword, select out of 700 headlines and edit the grammar if needed (which most probably will be the case).

3. WebX

This is a blog post idea generator, but feel free to use it for your email titles as well. The useful functionality the platform has is idea googling. Choose the option you like, click Google this idea and see what Google has on this topic.

4. ActiveCampaign

Choose a keyword category (Benefit, Topic, Pain Point) and enter your keyword. You can see 4 suggested subjects at a time. To see new combinations, click Generate more suggestions.

ActiveCampaign subject generator

5. Cold email subject line generator

A free tool by Reply that works similarly to ActiveCampaign. Choose one of 4 categories (Benefit, Problem, Personalized, COVID-19) and enter the keyword. Generate more suggestions if you can’t find the right one. All lines displayed in the window can be exported as an excel file.

All tools for marketing automation within one platform

6. Reply.io

Reply.io is a cold subject line generator that generates subjects by keywords for one of the selected categories - Benefit, Problem, Personalized, COVID-19. 

It also has AI-supported email quality check that estimates how likely your subject line is to receive a response. 

7. Hubspot

Enter up to 5 nouns to get 5 ideas for blog posts. Register to unlock 250 ideas that are promised to provide you for a year.

Hubspot subject generator

8. SEOPressor

This blog title generator can give you ideas on best subject lines for email marketing as well. Enter your keyword and select the category it’s more likely to belong to. It can be a generic term, event, location, etc. The tool shows 10 results at a time, but the suggestions are numerous. I entered email as a generic term and got 1,160+ titles. Many require optimization, you’ll get ideas to work on.

9. Mizy

Mizy is an AI-powered subject generator that offers you suggestions based on the copy of your email. It’s still available in the beta version but already can give you some nice lines.

Look at the copy and original subject line, and then at the option the program gave me. Not perfect, but you may get a better result with more text available.

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Subjects by Mizy

10. Headline and Subject Line Generator by Google

This is an extension you can use straight in your Gmail account. Can give you a hand when you send bulk emails with Gmail, write a corporate newsletter or want to get fancy when writing to your friends.

Choose between four categories – List, How To, Question, General – and enter the keyword or phrase. Gmail offers rather standard versions, but they’re all good and grammatically verified.

Subject by Google

What’s more, you can switch from Swipes to Headlines (top right corner). This tab also has four categories – Email Series, Promos, Blogging, E-commerce – but offers just general suggestions: you can’t enter your words here.

Last post

11. Tweak Your Biz

This platform has extra filter options in addition to regular key searching. Enter the word, specify if it’s a noun or verb and choose how you want your results to appear. Suggested options will be formed in categories, and they may differ depending on what you’re looking for.

I entered email and the results were grouped in the categories Lists, Questions, How to, Business, Celebrities, etc. However, the word vegetables generated other groups like Lists, Best, Love, Secrets.

12. FATJOE

Just your regular random subject line generator. Enter the word to see 10 suggestions. To see more, you need to register.

13. Kickass Headline Generator

An email subject generator by Sumo. It differs from the above platforms in that it doesn’t generate you ready suggestions. Instead, it gives formulas based on the conditions you set. You can choose the title format and then specify extra requirements like topic, audience, outcome, etc.

Kickass line generator

14. Content Row

This isn’t just a subject line creator but an entire content management tool. In addition to headline generation, you can use a headline analyzer, word counter, case converter, etc. A big disadvantage of the platform, though, is its limited usage. Free users are only allowed three headline generator searches per day. Unlimited usage requires a subscription to a PRO pricing plan.

15. Tools.FromDev

A title maker is only one of the services this platform offers to online developers. Go to SEO > Title Maker, enter the subject and check the results. The good thing that the tool can generate some good suggestions; the bad thing is that they aren’t displayed in a list. You need to keep on clicking Suggest Title to see every next combination.


The above platforms can really be helpful when it comes to creating subject lines. However, they only show you the direction to move in. The editing and final touches are always up to you. Don’t forget about grammar, spelling, SEO optimization, and relevance because even the best generator doesn’t know your audience and their likes.

Also, keep in mind that generators give you only text suggestions and rare numbers. Feel free to mix them with emojis, symbols and more specific digits.

And for a better marketing result, run regular A/B testing to determine which titles generate more clicks. In eSputnik, you can test email subject lines in two methods: within one email and with several emails sent to different segments.

The results are displayed in the campaign report in a separate tab. The winner option is highlighter green, and you can see what percentage advantage it had over competitors. Such tests help adjust marketing strategies and often may be the answer to the question “How to get my emails opened?”

Subject A/B test report in eSputnik

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Iuliia Nesterenko

Technical Writer

A technical (but still very creative) writer at eSputnik with a strong focus on design, current digital marketing trends, and new solutions for email automation.

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