How to Split Test SMS Marketing Messages

Why SMS Testing Is Different From Email Testing

Email testing typically focuses on open rates because getting someone to open your email is the first major hurdle. SMS does not have that problem. Nearly every text message gets read, usually within three minutes of delivery. This means the equivalent of "open rate" is essentially 100% for SMS, so your testing needs to focus on what happens after the message is read: click-through rates, reply rates, and conversion rates.

The character limit also changes what you can test. An email subject line test might compare a 30-character version against a 60-character version. In SMS, you are working within a much tighter space. Every word matters more, and the differences between your test versions need to be concentrated in fewer characters. This actually makes SMS testing more precise, because the variables you test are inherently more focused.

Response speed is another key difference. Email tests need 24 to 48 hours to accumulate meaningful data because people check email at different times throughout the day. SMS responses happen fast. Most clicks and replies come within the first 30 minutes of delivery. You can often evaluate an SMS split test within a few hours of sending, which means you can run more tests in less time.

What to Split Test in SMS Messages

Message Opening

The first few words of your text message determine whether the recipient keeps reading or swipes it away. Test different opening approaches: leading with the recipient's name versus leading with the offer, starting with a question versus starting with a statement, opening with urgency versus opening with curiosity. Because SMS is so short, the opening has an outsized impact on the entire message's performance.

Call to Action Placement

Test whether placing your link or call to action at the end of the message performs differently than embedding it in the middle. Some audiences scroll to the end and tap the link. Others engage more when the link appears right after the value proposition, before any additional context.

Personalization Level

Test messages that include the recipient's first name against messages that do not. Then test messages that reference specific past behavior ("Since you visited our site last week...") against generic messages. Personalization in SMS can feel more intimate than in email because text messages are inherently personal, so the impact of getting it right or wrong is amplified.

Tone and Formality

Test a conversational, casual tone ("Hey, quick heads up...") against a more professional tone ("We wanted to let you know..."). SMS as a channel skews casual, but your audience might prefer professional communication depending on your industry and the nature of your relationship with them.

Message Length

Test a single-segment message (under 160 characters) against a two-segment message (up to 320 characters). Shorter messages are cheaper to send and feel more natural for SMS. Longer messages let you include more context and a stronger value proposition. The right answer depends on your audience and your offer.

Setting Up an SMS Split Test

The mechanics are the same as email testing. Split your list randomly into two groups, send each group a different version of the message at the same time, and measure the results. The key differences are in timing and metrics.

For timing, you can check results much sooner than with email. If you send an SMS campaign at 10 AM, check click-through rates at 1 PM. By that point, the majority of people who are going to engage have already done so. For email, you would need to wait a full day.

For metrics, focus on click-through rate if your message includes a link, or reply rate if you are trying to start a conversation. Do not measure "delivery rate" as your test metric, because delivery rates reflect your phone number health and carrier relationships, not the quality of your message copy.

SMS Testing Pitfalls to Avoid

Do not test send times by sending version A at 9 AM and version B at 2 PM. That is a send time test, not a message test. If you want to test send times, send the same message to two groups at different times.

Do not run SMS tests too frequently on the same list. Unlike email, where people tolerate daily messages from some brands, SMS has a much lower tolerance for frequency. If you send multiple test messages in a short period, you risk opt-outs that have nothing to do with your message quality and everything to do with recipient fatigue.

Do not ignore opt-out rates in your analysis. If version A gets a higher click-through rate but also triggers twice as many opt-outs as version B, version A is not actually winning. The short-term clicks are not worth the long-term list shrinkage.