Every legitimate SMS marketing program has an exit door, and that door is labeled STOP. When someone replies STOP to your text, they are telling you to stop messaging them, and the rules say you must listen. Getting opt-out handling wrong is one of the fastest ways to rack up complaints, carrier blocks, and legal trouble.
This guide explains how SMS opt-outs work from both sides: what recipients should expect, and what senders must do. As always with compliance topics, this is general information, not legal advice. The rules evolve, so confirm current requirements with qualified counsel for your situation.
Why STOP exists
SMS is an unusually intimate channel. Messages arrive with a buzz in someone’s pocket, day or night. Because of that, regulators and the industry built strong consumer protections around it. The core principle is simple: anyone can leave any messaging program at any time, easily, and the sender must honor that immediately.
The standardized mechanism is the reply keyword. The recipient texts a word like STOP, and the sender’s system must recognize it, stop sending, and confirm. This is enforced at multiple levels: by industry guidelines from CTIA, by FCC rules, and by the carriers themselves, which can block your traffic if you ignore opt-outs.
The keywords you must honor
CTIA’s messaging guidelines require senders to support a set of standard opt-out keywords without exception: STOP, UNSUBSCRIBE, CANCEL, END, and QUIT. When your system receives any of these, it must stop future sends to that number and send a single confirmation message acknowledging the opt-out.
In practice, most platforms go further and recognize common variations: STOPALL, STOP ALL, and plain-language requests like “please stop texting me.” The direction of the rules is clear: if a reasonable person would read the reply as an opt-out request, treat it as one. Do not rely on exact-match keyword logic and hope the edge cases never get tested.
Capitalization, punctuation, and minor typos should not matter. “stop,” “Stop!,” and “STOP” are all the same request. Build your handling to be forgiving.
What the confirmation message should look like
After an opt-out, you may send exactly one confirmation message. It should be short, clear, and free of marketing content. Something like: “You have been unsubscribed and will no longer receive messages from [Your Business]. Reply START to resubscribe.”
That is the entire job of the confirmation. It tells the person the opt-out worked and how to reverse it if they change their mind. It must not contain promotions, upsells, or “are you sure?” persuasion. One message, then silence.
After the confirmation, no further marketing messages may go to that number unless the person affirmatively opts back in. “Affirmatively” matters: you cannot resubscribe someone because they bought something or because enough time passed. They need to take a clear action, like texting START, that shows they want your messages again.
Opt-outs beyond the keyword
Here is the part many senders miss: the keyword is not the only valid opt-out. FCC rules now require businesses to honor opt-out requests made through any reasonable method. If a customer emails you asking to stop texts, calls your support line with the same request, or writes “please take me off your text list” in a chat, that counts.
These non-keyword requests must be honored promptly, generally within ten business days, though processing them in real time is the recommended practice. This means your opt-out handling cannot live only inside your SMS platform. Whoever answers your phones, emails, and chats needs to know how to route a text-message opt-out into your suppression system.
For keyword replies themselves, the expectation is effectively immediate. When someone texts STOP, your system should suppress that number before the next send goes out. Batch-processing opt-outs once a week is not compliant.
HELP is the other keyword to get right
Alongside STOP, your program should support HELP. When someone texts HELP, reply with useful information: what your program is, how often you message, that message and data rates may apply, how to get support, and how to opt out. It is a small thing, but it is required by industry guidelines and it defuses confusion before it becomes a complaint.
A typical HELP reply: “[Business Name]: You are subscribed to order updates, up to 4 msgs/month. Msg and data rates may apply. Reply STOP to opt out. Questions? Call [number].”
Where opt-out language must appear
Recipients cannot use an exit they do not know about. Opt-out instructions need to appear in the right places:
In your call to action. Wherever you invite people to opt in, on a form, at checkout, in an ad, the disclosure should mention that they can reply STOP to opt out. Consent language and opt-out language travel together.
In your opt-in confirmation. The first message someone receives after subscribing should identify your business, describe the program, and explain how to opt out. This is the message that sets expectations for everything after it.
Periodically in ongoing messages. For long-running programs, remind recipients how to opt out from time to time. A short “Reply STOP to end” on a regular message costs you a few characters and prevents a lot of frustration.
In your terms and privacy policy. Your full messaging terms should document the opt-out process alongside everything else about the program.
Common opt-out mistakes
The most common failure is simply not processing opt-outs fast enough. A STOP reply that sits in an inbox until someone manually updates a spreadsheet is a violation waiting to happen. Automate it.
Next is the “one more message” temptation. After someone opts out, do not send a farewell promotion, a feedback survey, or a win-back offer. The confirmation message is the last message. Full stop.
Another mistake is treating opt-outs as campaign-specific when they should be broader. If someone opts out of your promotional texts, think carefully before continuing to send them other automated messages. When in doubt, suppress broadly and let them re-opt in to what they want.
Finally, do not forget about quiet hours in your opt-out handling. Even your confirmation message should respect timing rules. Nobody wants their unsubscribe confirmation at 2 am. Check the rules for your recipients’ states with our SMS quiet hours by state guide.
What recipients should know
If you are on the receiving end, the system is designed to protect you. Replying STOP to an unwanted marketing text should stop the messages. If they continue, you can report the sender to your carrier by forwarding the message to 7726 (SPAM), and you can file complaints with the FCC. Legitimate businesses honor opt-outs because the alternative is expensive for them.
One caveat: STOP only works for the sender that sent the message. If you get texts from three different businesses, you need to opt out of each one separately.
Frequently Asked Questions
What is the difference between STOP and STOPALL?
STOP opts you out of the program that sent the message. STOPALL is a broader request meant to stop all messages from that sender. Most platforms treat them similarly, but if you run multiple programs, make sure your system handles the broader request correctly.
How quickly must I process a STOP request?
Keyword opt-outs should be processed effectively immediately, before your next send. For opt-out requests made through other channels like email or phone, FCC rules generally require honoring them within ten business days, with real-time processing recommended.
Can I text someone who opted out if I have news they might want?
No. An opt-out means no marketing messages until they affirmatively re-opt in. There is no exception for messages you think they would like.
Does STOP work for transactional messages too?
A STOP reply should be treated as a request to stop automated messages from that sender. Be careful about continuing to send even transactional texts to someone who just told you to stop. When in doubt, suppress and let them re-subscribe.
What should my opt-in confirmation message include?
Your business name, a description of the program, message frequency, the “message and data rates may apply” disclosure, and opt-out instructions. Getting this message right sets up your whole program for compliance. See our SMS campaign checklist for the full pre-send rundown, and use sample campaign descriptions as a reference when registering.
Opt-out handling is one of those things that is simple to describe and easy to get wrong in practice. Automate it, test it, document it, and respect it. Your deliverability and your legal standing both depend on that little four-letter word working exactly as promised.