A/B Testing SMS: What to Test and How to Measure

SMS campaigns often report delivery and open rates. Those metrics matter, but they are not the job. The job is action: pay, sign up, upload, reply, redeem, return.

A useful A/B test compares two versions of a message sent to similar audiences under similar conditions. Version A might emphasize a deadline; Version B might emphasize ease of payment. Version A might send at 9 a.m.; Version B at 2 p.m. The key is to change one strategic element—not everything at once.

What to test in SMS:

Timing and day of week—when is the customer most likely to act?

Opening line—does the first sentence create salience (amount, date, consequence)?

Call to action—one link, one verb, one next step?

Length—does brevity reduce friction or remove needed context?

Tone—formal reminder versus supportive nudge (match your brand and regulatory context).

Social proof or trust cues—where appropriate, does a short trust line help?

What to hold constant: audience definition, channel, and—where possible—the business rules behind the journey. If you change audience and message simultaneously, you will not know what caused the result.

Sample size is a practical constraint for many businesses. You may not reach statistical significance quickly. That does not mean testing is useless. It means you should interpret directionally, repeat tests, and combine qualitative signals (support calls, customer replies) with quantitative ones.

Avoid common traps: stopping a test too early because one version "looks" better; testing emoji or punctuation alone when the real barrier is clarity; and declaring victory on clicks when revenue or completion is flat.

Hub is being built to support this discipline—templates, variants, and reporting tied to outcomes. Until then, the same principles apply in any SMS tool: hypothesize, split, measure action, learn, iterate.