String Identifier (SID)
A String Identifier (SID) is a unique key that is used to identify specific resources.
String Identifiers at Twilio
Every Twilio resource has a 34 digit SID. You can use the first two characters of the SID to identify its type. Many of our API calls will return a JSON object containing another resource’s SID. Using this SID, you can retrieve more information about the specific resource.
For example, the following code creates an SMS message:
Note how the newly created message has a property named sid. Using this value we can later fetch this specific message.
Using the message SID, which is prefixed with MM, we were able to get more information about that specific resource.
Common SID Prefixes
Twilio’s product offering is expansive. Products range from Voice and video, Messaging, chatbots, Internet of Things connectivity, and security. Therefore, you’ll encounter many resources along your journey.
Below is a table of the most commonly-seen SID prefixes:
| Prefix | Resource Type |
| AC | Account |
| CA | Call |
| CF | Conference |
| HS | Device (Super SIM) |
| MM | Message |
| PA | Conversation Participant |
| QU | Queue |
| SD | SIP Domain |
| YC | Authy Challenge |
