A short code is a 5-6 digit phone number that businesses use to deliver text messages to their customers. Short codes have a higher throughput than toll-free numbers, so if your business needs to send SMS messages to more than 30,000 people at a time or relies heavily on MMS, we recommend upgrading from a complimentary toll-free number to a short code. Once you reach the recommended sending volume, Klaviyo will reach out to help you secure a dedicated short code for your business. If you want a short code before reaching 30,000 people, you can request a short code and begin using it as soon as the application is approved by mobile carriers. The short code will come at an additional cost. Some brands choose to start sending from a short code immediately to prevent having to change the number that customers receive their texts from when migrating from a toll-free number to a short code.