Do you send SMS through Twilio?

While the information on this page typically applies to anybody who sends SMS messages, we can only guarantee that it applies to users who manage their SMS senders and billing through Customer.io. Your mileage might vary if you obtain phone numbers and manage billing through Twilio.

# Opt-in and out flow

You need to provide your users with clear instructions to opt into and out of your SMS messages. You must have designs for your opt-in and out flow before you request a sender number. Twilio and carriers evaluate your opt-in and out flow as part of your registration process.

## You must preview your opt-in and out flow before you register as an SMS sender[](#you-must-preview-your-opt-in-and-out-flow-before-you-register-as-an-sms-sender)

You do not need to have completed your opt-in and out flow before you contact Customer.io to register as an SMS sender—in part because you won’t be able to do it until you have a sender number!

But you need to have designs or a preview to demonstrate your opt-in and out flow. Twilio and carriers evaluate your designs to make sure that you’re ready to send messages.

## What format should my opt-in and opt-out preview be?[](#what-format-should-my-opt-in-and-opt-out-preview-be)

It’s a best practice to have your opt-in and out flow in a live, preview-able state. It doesn’t need to be publicly accessible; you might place your opt-in flow on a staging website or otherwise hide it from your public site. But providing a functional URL makes it easier for Twilio and cellular carriers to preview and test your opt-in flow.

If that won’t work for you, a PDF design of your opt-in and out flow is sometimes an acceptable alternative.

## Writing opt-in and opt-out instructions[](#writing-opt-in-and-opt-out-instructions)

We partner with Twilio to send SMS messages. By default, Twilio [supports a number of keywords](https://help.twilio.com/articles/223134027-Twilio-support-for-opt-out-keywords-SMS-STOP-filtering-) to opt into or out of messages. You may want to use their list of keywords in the opt-in and opt-out instructions that you add to your [privacy policy](#update-your-privacy-policy).

Beyond your privacy policy, you should make sure that you already gather explicit consent for marketing messages—even before you request a sender phone number. This is often something like a checkbox on your signup form that allows users to explicitly opt-in to receive marketing messages—assuming you send marketing messages.

### Example opt-in and out flow[](#example-opt-in-and-out-flow)

For example, you might include the following with a checkbox on your site:

Explicit Opt-in Example

By entering your phone number and checking the box, you agree to receive marketing messages from <Business name> at the phone number provided above. You may receive up to 4 messages per month. Data & message rates may apply. Reply STOP to opt out and HELP for help. \[Privacy Policy Link\] \[Terms of Service Link\]