10 Best Email A/B Testing Tools for Founders [2026 Updated]

1. Klaviyo

• Type: Paid
• URL: https://www.klaviyo.com
• Overview: Klaviyo provides built-in A/B testing for email campaigns and flow messages, letting you test subject lines, content, send times and automatically select winners. It includes advanced analytics and options to automatically send the winning variant to remaining recipients or personalize variant delivery per customer behavior.

2. Mailchimp

• Type: Paid
• URL: https://mailchimp.com
• Overview: Mailchimp supports A/B testing of subject lines, from names, content, and send times within campaigns and automations to identify higher-performing variants. It provides test configuration controls, winner selection, and performance reporting to optimize future sends.

3. ActiveCampaign

• Type: Paid
• URL: https://www.activecampaign.com
• Overview: ActiveCampaign enables split testing across campaigns and automation streams, allowing tests of subject lines, email content, and sending rules while tracking opens, clicks and conversions. Its automation-first approach lets you run tests inside multi-step journeys and act on winners automatically.

4. Campaign Monitor

• Type: Paid
• URL: https://www.campaignmonitor.com
• Overview: Campaign Monitor offers A/B testing for subject lines, content and send times with easy setup and reporting to determine winning variants. It integrates with segmentation and personalization features so you can run targeted experiments on defined audience segments.

5. Brevo (formerly Sendinblue)

• Type: Free
• URL: https://www.brevo.com
• Overview: Brevo includes A/B testing tools for subject lines, sender info and email content and can automatically pick winners based on open or click performance. It offers both campaign and transactional email testing, plus workflow-level split testing inside automations.

6. Twilio SendGrid

• Type: Paid
• URL: https://sendgrid.com
• Overview: SendGrid supports A/B testing for campaign sends — including subject lines and content variations — with reporting on deliverability, opens and clicks to choose the best performer. It’s focused on high-volume senders and integrates A/B tests into API-driven or UI-managed campaigns.

7. Litmus

• Type: Paid
• URL: https://www.litmus.com
• Overview: Litmus specializes in pre-send testing and analytics, offering A/B testing capabilities for subject lines and email content alongside rendering checks and inbox previews. It helps you validate variants across clients and measure engagement signals to pick the most effective version.

8. Email on Acid

• Type: Paid
• URL: https://www.emailonacid.com
• Overview: Email on Acid provides A/B testing support for subject lines and content combined with comprehensive inbox rendering previews and QA tools. It emphasizes delivering variant comparisons with deliverability and viewability insights so you can choose the best-performing email.

9. Omnisend

• Type: Paid
• URL: https://www.omnisend.com
• Overview: Omnisend offers A/B testing for campaigns and automation messages allowing tests of subject lines, content blocks and send times, plus automated winner selection. It combines testing with e‑commerce-focused segmentation and conversion tracking for revenue-driven experiments.

10. MailerLite

• Type: Free
• URL: https://www.mailerlite.com
• Overview: MailerLite includes A/B testing for subject lines, content and sending times within campaigns, aimed at small teams and cost-conscious senders. It provides simple setup, winner selection and basic performance reporting to help iterate quickly on email creative.