db.models.Field.null

Field.null

If True, Django will store empty values as NULL in the database. Default is False.

Avoid using null on string-based fields such as CharField and TextField because empty string values will always be stored as empty strings, not as NULL. If a string-based field has null=True, that means it has two possible values for “no data”: NULL, and the empty string. In most cases, it’s redundant to have two possible values for “no data;” the Django convention is to use the empty string, not NULL.

For both string-based and non-string-based fields, you will also need to set blank=True if you wish to permit empty values in forms, as the null parameter only affects database storage (see blank).

If you want to accept null values with BooleanField, use NullBooleanField instead.