ERROR 001624: Failed to alter field length

Error Message

In ArcGIS Pro, attempts to alter the field length for a field in an attribute table fail, and return the following error message,

Error:
ERROR 001624: Failed to alter field length

Cause

A smaller value is entered to decrease the field length. This is a known limitation. In ArcGIS Pro, while the field length of a field can be increased to include larger values, it is not possible to reduce the field length by specifying a value smaller than the existing value. For example, if the existing field length is 255, the error message is returned when attempting to alter the field length to 250.

Solution or Workaround

Create a new field with a smaller length field value and repopulate the new field. Refer to How To: Decrease the character length for a text field in ArcGIS Pro for instructions.