ECI allows data streams with different interpretations to be encoded in one symbol. Without ECI the default interpretation is ISO8859-1, the Latin alphabet used in western Europe. Started from version 3.30, the ECI is supported on DataMatrix Fontware.

An ECI value can be any number between 0 and 999999. The tilde code ~7nnnnnn is used to enter the ECI value. The tilde code sequence can appear at any places of the input, but there must be exact 6 digits following ~7. For example, to start ECI interpretation 10, enter ~7000010.