Each call will generate one or more Call Detail Record (CDR). CDRs are written after the call ends, and contains all information needed for accounting and billing that call. As an example, an outbound call (outbound is most critical for accounting and billing) the CDR would contain information such as date/time, caller account, caller device, destination, and duration. As an added bonus it can contain all kinds of details about the call itself, such as codec used, outbound route or gateway, and/or the status of the system.

So, in CDRs you can store and gather any kind of info you deem useful on a per-call basis. A complete call is often composed of an A leg (caller) bridged to a B leg (callee). In the FS console, the show calls command shows that each call is composed of two channels (A leg and B leg). You can choose to write a CDR for A leg, B leg, or both.

There are two main kinds of CDRs FreeSWITCH is able to generate: Comma Separated Value (CSV) files, and XML files...