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# Custom Field Handling
### Custom Fields
Any custom fields you have defined through document customization are automatically included in REST API definition. There is specific naming convention that is a combination of the Custom Code you created via document customisation plus the internal field name concatenated with an underscore. i.e. {customization code}\_{field name}
Document customization screen showing the user definable Customization Code
*Document customization screen showing the internal field names:*
Response from a GET call to fetch a Work Order that shows custom fields:
### Custom drop-down fields with additional attributes
Users can enable **custom dropdown fields** (through enabling a document customisation flag 'Additional API details', so that when called by the REST API will return the additional attributes stored with the dropdown record such as external\_key.
Document Customisation fields showing additional checkbox:
Example of a custom drop-down field when 'Additional API details' is not enabled:
Example of a custom drop-down field when 'Additional API details' is enabled:
