What is SMS Opt-In / Opt-Out?

SMS Opt-In and Opt-Out are the consent mechanisms that govern business text messaging. Opt-in is the process by which a consumer gives explicit permission to receive texts from a brand. Opt-out is how they withdraw that permission — most commonly by replying STOP to any message.

Under the TCPA, businesses must obtain prior express written consent before sending marketing texts. This consent must be affirmative (the customer takes a deliberate action), informed (they know they're agreeing to receive texts), and documented (you can prove consent was given).

Opt-out must always be available and honored immediately. When a customer replies STOP, the business must cease all marketing messages to that number. Continuing to text after a STOP reply is a TCPA violation with penalties of $500–$1,500 per message.

Common opt-in methods include: keyword opt-in (texting a word to a short code), web form opt-in (entering a phone number on a website with consent language), checkout opt-in (checking a box during purchase), QR code opt-in (scanning a code that pre-fills a text), and verbal opt-in (with proper documentation).

For opt-in to be TCPA-compliant, the consent language must clearly state: the customer is agreeing to receive marketing texts, the identity of the sender, that message and data rates may apply, and that they can opt out at any time by replying STOP.

Opt-out is handled automatically by SMS platforms. When a subscriber replies STOP (or UNSUBSCRIBE, CANCEL, END, QUIT), the platform immediately flags the number as opted-out and suppresses all future marketing messages. Brands must not manually override opt-outs.

Proper opt-in and opt-out handling isn't just compliance — it's the foundation of a healthy SMS program. Subscribers who actively opted in are more engaged, more likely to purchase, and less likely to complain. Purchased or scraped lists lead to high opt-out rates, carrier complaints, and legal exposure.

Opt-out handling directly affects deliverability. Carriers track complaint rates per sender. If your opt-out rate or spam complaint rate is high, carriers will filter your messages — reducing deliverability for your entire program.

For SMS commerce, clean consent means every subscriber genuinely wants to hear from you. This self-selected audience is why SMS converts so much better than interruptive channels. Protect that asset by respecting opt-in and opt-out rigorously.