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Course Content - Intermediate

Call Recordings


Welcome to the online training series from 3CX. This module will cover the call recordings of 3CX.


In this module we will see the various aspects of the recordings in 3CX. We will see the control of the recordings, where they can be stored, their format as well as how much space the recordings can take on the server.

We will finish this module with some backup tips, to make backing up and restoring easier.


Depending on the nature of the corporation, the way calls are recorded may differ. Some companies may want all calls to be recorded by default, while others only require external calls to be recorded by default. This is an option which is up to the admin to configure on the extensions. In addition to this, the admin can also prevent an extension user from starting or stopping the recordings on the fly, and force the user of the extension to follow the configured behaviour defined, that being recordings off, recording all calls or recording only the external calls, without any interaction by the extension user. This however is a feature only available in the Enterprise edition of 3CX.


Call recording files can only be saved on storage units defined as local units by the Operating System, like a local hard drive, an iSCSI drive, or a Storage Area Network unit. This should not be confused with the Network Attached Storage.


Speaking of drives, this is a resource which can very easily get consumed and filled up. The overfilling of the drive can be prevented by using a few configuration options which will allow the admin to control the use of the drive space. First of all, the admin can configure how much of the drive will be consumed with the recordings. The quota can be configured from the recordings page, and clicking on Quota. The default quota for the recordings in Version 15.5 is 5 Gigabytes. The quota which you had from a previous version will not be valid in Version 15.5, as this is not carried over when a backup is restored.

When the recording quota is nearing to be filled up, an email notification will be sent to the admin.

Sometimes recordings need to be kept for legal purposes, but there are some cases where legal restrictions are not enforced. In this case the recordings which are over a certain age, can be deleted.


All audio files in 3CX, which also includes the recordings, need to be in a particular format. The audio files are WAV files, encoded as 8kHz, 16 bit, Mono files. The recordings can now be encoded in either PCM or ADPCM. PCM generally takes up about 1MB of disk space per minute of recording, and can be played on all media players.

Adaptive PCM, or ADPCM is a more compressed format, and generally takes up about 256KB of disk space per minute of recording. Due to the nature of the compression, some media players, and in particular mobile or browser based media players have difficulty playing these types of files.


Apart from taking a significant amount of space on the hard drive, the recordings can also swell up the size of the backups as well. This will cause delays in the restoring of the backups, as all these recordings will need to be copied from the backup file to disk.

There is a bit of good news however, as these can be copied to a different local disk, away from the main local drive of the PBX. When a backup is taken, the recordings will not be included in the backup, but they will remain on the secondary disk. When the backup is restored, the recordings will be mapped at their location and will be visible.

This will allow the backup file to be a much smaller size. You will also be able to backup the files separately, using your own software even.

Keep in mind, however, that when changing the location of the recordings, and putting them on a separate drive, that the recording folder is not the root folder of the disk. Just create a recordings folder and define this as the recording file location.


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