A log analytics graphical user interface enables a user to dynamically extract and define a field from unstructured log data. The log analytics module automatically determines a definition for a field based on log text selected by the user. A portion of each log message is highlighted to reflect what the extracted field may be to assist users with understanding if input parameters are selected the intended log data. Changes to the definition of the field, by the user, may cause further highlighting that to indicate an incomplete or erroneous field definition.