SMS opt-in: build the consent text and see who asks for each part
SMS opt-in is a person's consent to receive texts from a business, collected before the first text is sent. This builder assembles your consent language and your confirmation message from what you enter, and counts the confirmation's segments. The sources behind it are the FCC's rule, CTIA's guidelines, T-Mobile's Code of Conduct and the 10DLC requirements Twilio and Bandwidth publish, read September 28, 2026.
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SMS opt-in builder
Consent text beside your opt-in
By checking this box, I agree to receive recurring automated marketing text messages from Main Street Dental about appointment reminders and offers at the number provided. Up to 4 msgs/month. Consent is not a condition of purchase. Msg & data rates may apply. Reply HELP for help, STOP to cancel. Terms: example.com/sms-terms. Privacy: example.com/privacy.
Confirmation text sent after opt-in
Main Street Dental: You are subscribed to appointment reminders and offers. Up to 4 msgs/month. Msg & data rates may apply. Reply HELP for help, STOP to cancel.
160 characters, GSM-7: billed as 1 SMS segment.
| Element | In your texts | What each source says |
|---|---|---|
| Brand or sender name | Yes | |
| What the messages are about | Yes | |
| The number or short code the texts come from | No |
|
| How often messages are sent | Yes | |
| "Msg & data rates may apply" | Yes | |
| How to opt out (STOP) | Yes | |
| How to get help (HELP) | Yes | |
| Link to terms and conditions | Yes | |
| Link to a privacy policy | Yes | |
| A consent box left unchecked, apart from other terms | On your form: leave it unchecked | |
| Written consent to automated marketing texts | Yes | |
| Consent is not a condition of purchase | Yes |
|
| A confirmation text after opt-in | Yes, the second text |
The builder assembles wording from what you enter and shows what each published source names. It does not review a program, and a carrier or provider decides whether a campaign is approved.
What SMS opt-in is
SMS opt-in is the consent a US business collects before it texts a person. The consent can be given on a web form or by text. The FCC distinguishes two kinds of text in its consumer guide: commercial texts need written consent, while informational texts may rest on oral consent. The carriers and the 10DLC providers add their own checks on top of the FCC's rule. This page carries a builder that turns those published requirements into text you can read and edit.
What the rules and the carriers ask for
The law here is the FCC's. Under 47 CFR 64.1200, a marketing text sent with an autodialer to a mobile number needs prior express written consent: a written agreement, signed by the person with an electronic signature permitted, that authorizes the seller to deliver such messages to the number given, and it must say the person is not required to agree as a condition of buying anything.
CTIA's Messaging Principles and Best Practices are industry guidance. CTIA says a call-to-action should show the program or product description, the terms and conditions, how to opt out, and any fees or charges, phrased as "Msg & data rates may apply", with privacy policies referenced in and accessible from it. T-Mobile's Code of Conduct, version 2.2, says the sender must send a confirmation message on receiving consent, and recurring programs must show opt-out instructions at opt-in and at regular intervals. Twilio's 10DLC pages say opt-in language must state message types and frequency, carry the rates disclosure and the opt-out, and on a website link a privacy policy and terms, with a consent checkbox unchecked by default. Bandwidth's vetting requirements add the brand name and a privacy policy that says mobile opt-in data will not be shared with third parties for marketing. The wider SMS compliance rules and 10DLC registration pages carry these in full.
The confirmation text
CTIA's Short Code Monitoring Handbook, version 1.9, says recurring programs send a single opt-in confirmation message showing the program name, customer care contact, message frequency, the rates disclosure and how to opt out. T-Mobile's Code of Conduct, version 2.2, says the sender must send a confirmation message on receiving consent. T-Mobile also recommends a second, double opt-in when consent was first collected outside SMS, for example on paper or a website form. The builder assembles the confirmation from what you enter, and counts its segments with this site's character and segment counter so you can see what the message costs to send.
SMS opt-in questions
Do you need written consent to send marketing texts?
The FCC's rule at 47 CFR 64.1200 requires prior express written consent for a marketing text sent with an autodialer to a mobile number. That consent is an agreement signed by the person that authorizes the seller to text the number given. Informational texts may rest on oral consent, the FCC consumer guide says.
What should an SMS opt-in message say?
The published sources name these elements: the brand name, the types of messages, the message frequency, "Msg & data rates may apply", how to opt out, and links to terms and a privacy policy. Twilio and Bandwidth list these in their 10DLC requirements; CTIA lists the program or product description, the terms and conditions, how to opt out, and any fees or charges.
What is double opt-in for SMS?
A second confirmation step. T-Mobile's Code of Conduct, version 2.2, recommends a double opt-in when consent was first collected outside SMS, for example on paper or a website form.
Can people opt in by texting a keyword?
T-Mobile's Code of Conduct, version 2.2, names a texted advertising keyword as one of its examples of opt-in. The builder takes a keyword as its opt-in source. The SMS keywords page lists which scored providers publish text-to-join keywords and what they charge for them.