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# Apply refiner

> Reformat extracted data according to your specifications.

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The *Apply refiner* step reformats extracted data according to your specifications, using a linked refiner module.

Refiner is a post-processing tool that takes raw model or agent extraction output and transforms it into the format required by downstream systems and validation rules. It operates on a spreadsheet-like interface where each row is a processed record and each column is a field.

Refiner provides a rich function library organized by category:

* String functions -- trimming, splitting, replacing, formatting text values

* Numerical functions -- arithmetic, rounding, unit conversions

* Table functions -- manipulating extracted tabular data

* Logical functions -- conditional logic, branching, null handling

* Parsing functions -- date parsing, currency parsing, structured text parsing

* Validation functions -- type checks, range checks, format validation

UDFs can also be called from within refiner for custom logic that exceeds the built-in function library. Learn more in [Creating refiner programs](/flow/step-config-reference/creating-refiner-programs).

## Parameters

* **Input file type** -- Specifies the source file format for the data you're refining. The default, **IBOCR**, is a JSON file that represents the output for most flow steps. In typical flows, IBOCR is the appropriate choice. If you're refining data that you've exported to CSV files, select CSV.

* **Refiner program** -- Select a refiner program. The refiner must be listed in the **Modules** panel to display as an option.