A short code is a special 5 or 6 digit telephone number that's shorter than a full phone number. Short codes are used to send and receive SMS and MMS messages to and from mobile phones. Twilio currently offers short codes in the US, Canada, and the UK.
If you're sending more than a few hundred messages a day from a long code, your messages run the risk of being marked as spam. Short codes are pre-approved by carriers to have a high throughput. This makes them perfect for sending those high-volume or time-sensitive messages. Here are some ways they're being used by developers:
There are two costs to consider when planning to use a short code:
There are two types of short codes: vanity and random. A vanity short code is a specific number that you choose, while a random short code is assigned to you and can’t be reviewed in advance.
Twilio short codes can send 100 messages per second by default; this limit can be raised for an additional fee. Because short codes can send high volumes of messages, wireless carriers individually approve every short code for its intended use. This approval process typically takes 8 to 12 weeks.
Short codes must be leased from a national registry for a minimum of three months at a time. Twilio will lease a short code on your behalf from this registry, unless you prefer otherwise.