> For the complete documentation index, see [llms.txt](https://docs.plumvoice.com/dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.plumvoice.com/dev/plum-dev-guide/sms-guide/industry-standard-short-codes.md).

# Standard Short Codes

## Industry Standard SMS Short Code Messages

Industry standard short code messages gives end-users control over the communications they receive from businesses. More information about proper use of these protocols is available in the [Short Code Monitoring Handbook](https://www.wmcglobal.com/hubfs/ctia-short-code-monitoring-handbook-current-Short-Code-Monitoring-Handbook-v1.7.pdf?hsLang=en).

#### Cheat Sheet

| Function | Default | Additional Options                      |
| -------- | ------- | --------------------------------------- |
| Opt-Out  | STOP    | CANCEL, END, QUIT, STOPALL, UNSUBSCRIBE |
| Opt-In   | START   | UNSTOP, YES                             |
| Help     | HELP    | INFO                                    |

### Opt-Out

The opt-out protocol removes an end-user from a sender's distribution list. Users who opt out of SMS messages are added to a blacklist and receive a message confirming their opt-out decision.

The default opt-out message is:

> You have successfully been unsubscribed. You will not receive any more messages from this number. Reply START to resubscribe.

* The SMS sender can use received opt-out messages (e.g., "Stop") to keep track of end-users who opted out of SMS notifications or for any other relevant purpose. 
* Following an opt-out, any attempt to send a SMS message sent to the end-user from the sender's distribution list generates an error response from Plum (example below). However, the end-user remains able send SMS messages to the sender.
* This behavior continues until the user explicitly opts-in to SMS notifications again.

```javascript
{
   "status":"failure",
   "error":"Error sending sms request"
}
```

#### **Opt-Out Keywords**

The default keyword to opt-out is **STOP**. The default keyword is always available, even if you instruct end-users to use a different keyword.

Use any of the following keywords in addition to STOP to enable end-user opt-outs: 

* CANCEL, END, QUIT, STOPALL, UNSUBSCRIBE

### Opt-In

The opt-in protocol is for end-users who opted-out of SMS messages previously and would like to resume receiving SMS messages from the sense. End-users receive an automated reply when they choose to opt back in to a sender's distribution list.

The default opt-in message is:

> You have successfully been re-subscribed to messages from this number. Reply HELP for help. Reply STOP to unsubscribe. Msg\&Data Rates May Apply.

* Although this protocol is intended for users who have opted-out of a given distribution list previously, any end-user that sends an opt-in message to the sender receives the automated reply, even if that individual was not a prior recipient.
* Plum customers see all incoming incoming opt-in messages. You can use this information to update customer data as necessary.

#### **Opt-In Keywords**

The default keyword to opt-out is **START**. The default keyword is always available, even if you instruct end-users to use a different keyword.

Use any of the following keywords in addition to START to enable end-user opt-ins: 

* UNSTOP, YES

### Help

The help protocol sends an automated help message to the end-user. 

The default help message is:

> Reply STOP to unsubscribe. Msg\&Data Rates May Apply.

* Plum customers are unable to see when end-users send a 'help' message.

#### **Help Keywords**

The default keyword to opt-out is **HELP**. The default keyword is always available, even if you instruct end-users to use a different keyword.

Use the following keyword in addition to HELP to provide assistance to end-users: 

* INFO