How to A/B test an email campaign
Web
Updated Aug 2026
Not sure which subject line or message works better? A/B test a campaign: RushFlow sends two versions to a share of your audience, measures which does better, and lets you send the winning version to everyone else.
Step by step
- Write your campaignCompose the campaign as usual (this is version A).
- Turn on A/B testSwitch on A/B test and enter variant B’s subject and/or message. Leave either blank to reuse version A’s.
- Choose the test sizeSet what share of the audience takes part in the test. The rest is held back for the winner.
- Send the testSend now. The test share is split evenly between A and B, and each person gets one version.
- Promote the winnerOnce opens and clicks come in, use promote winner to send the better-performing version to the held-back remainder.
How the winner is decided
The winner is the version with the higher click rate (tie-broken by open rate). You can also force a specific version if you prefer.
Good things to test
- Two subject lines
- Two offers or calls to action
- A short message versus a longer one
Frequently asked questions
How does A/B testing pick the winner?
By click rate (tie-broken by open rate). You can also choose the winning version yourself.
Does everyone get the test versions?
No. You set what share of the audience takes part in the test; the rest is held back until you promote the winner to them.
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