Caller IDs passed from carrier to carrier when a call is transmitted. When Twilio receives an incoming call, we perform basic normalization to display the incoming caller ID using standard E.164 formatting.

Unfortunately, different carriers vary in their preferred caller ID formatting. Since calls may traverse through several networks before reaching Twilio, the caller ID information may be altered along the way. In this situation, Twilio will pass along the caller ID (From) information exactly as we receive it from the calling party. It is currently not possible to discover the real caller ID once it has been altered by carriers.

There are three main circumstances that cause a caller ID to be displayed incorrectly:

• The originating carrier may have incorrectly formatted or not transmitted the original "From" number. This usually results in a missing caller ID, or a "translated" number code. For more information, please see Why am I getting calls from these strange numbers?
• A caller ID may be modified along the way by any intermediary carriers
• The caller ID may be lost or replaced when crossing international borders

Notice: For international calls, local regulations sometimes dictate that a caller ID be modified. We see this especially often with calls from Australia, for instance. Another example of this modification occurs when calls are initiated outside of the USA to Twilio toll-free numbers. For more information, please see Local Caller ID (CLI) international compatibility.