A short code is a special telephone number designed for high-throughput, two-way messaging. Short codes are used to send and receive SMS and MMS messages to and from mobile phones. Twilio currently offers short codes in multiple countries. Their name is derived from the fact that they are shorter (usually five to six digits) than their ten-digit long code counterparts.
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 and are not subject to carrier filtering. This makes them perfect for sending those high-volume or time-sensitive messages. Here are some ways they’re being used by developers:
Receive an SMS message and don't know who it's from? Want a short code, but find out it's unavailable? Use a short code lookup tool to find the owner. It'll tell you when it was registered and who registered it. It'll also tell you what to text to unsubscribe from their messages.
There are two costs to consider when planning to use a short code: