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Model parameters

Any model variable can be made a model parameter. There are two primary reasons to make a model variable a parameter.

  • Output variables that are set as model parameters are added to the map when the model is run inside ModelBuilder.
  • Variables that are set as model parameters show as tool parameters when the model is run as a geoprocessing tool, allowing you to specify different data or values for your model to process than what was specified when the model was created.
Model Parameters and Tool Dialog box

Create model parameters

To make a model variable a parameter, the model must be edited in ModelBuilder. In ModelBuilder, right-click any variable and select Parameter. When a variable is made into a parameter, a letter P appears beside the variable in the model.

The name of the variable is used as the model tool parameter label. You can rename a model parameter by renaming the model variable in ModelBuilder. Right-click the variable, select Rename, and enter the new name. When you open the model tool in the Geoprocessing pane, the parameter name will be changed. The value of a variable is used as the default value for the corresponding model tool parameter. If the variable has no value in ModelBuilder, thenthe tool parameter will be blank.

If you need the outputs of your model tool to appear in Geoprocessing History, you must make those outputs model parameters. For example, if your tool outputs an HTML file and you want the user to be able to click to open the file from Geoprocessing History, you must make the HTML output file a model parameter.

Model parameter properties

You can change several properties of model parameters using the model Properties window. These properties impact how the parameters will appear when the model tool is opened in the Geoprocessing pane.

Right-click any model in a toolbox and select Properties, or if you are editing the model in ModelBuilder, click the Properties button in the ribbon.


Change the order of parameters by dragging and dropping the parameters to the desired order in the Parameters tab of the tool Properties window.

Required or optional

Tool parameters can be required or optional. The designation for optional or required parameters happens automatically based on how the parameter is used in the model (for example, if the variable is used as the input to a required parameter of a tool in the model, then that model parameter will be required). You can change model parameters that ModelBuilder designates as optional to be required for the model tool, but you cannot set required parameters to be optional.

To change an optional parameter to a required parameter, set the Type of an optional parameter to Required in the Parameters tab of the tool Properties window.


Parameters can be assigned a category. Parameters in a category are displayed in a drop-down section when the tool is opened in the Geoprocessing pane.


Parameter filters are used to limit or restrict the input values or data that can be specified for a model tool parameter. For example, a Value List filter requires that only values from a list can be specified for the parameter. Values entered into a parameter that do not match the filter will raise an error; the model cannot be executed until a valid value is entered.

The following filters are available.

  • Value list—A list of predefined keywords. You can set a value list filter for string and numeric model parameters.
  • Range—The minimum and maximum numeric value. The range is inclusive, meaning both the minimum and maximum are valid choices.
  • Feature class—A list of allowable feature shape types, including point, multipoint, polyline, polygon, and multipatch.
  • File—A list of valid file extensions such as .txt or .gpx.

    Do not enter the period for the extension. For example, enter txt, not .txt. Separate list values with a semicolon (;). For example, to allow both .txt and .csv files, enter txt; csv.

  • Field—A list of allowable field types, including short, long, single, double, test, date, OID, geometry, BLOB, raster, GUID, global ID, and XML.
  • Workspace—The type of allowable workspace, including file system, local geodatabase, and enterprise geodatabase.


You can make one parameter dependent on another parameter. The most typical use for this is to make one parameter that accepts an attribute field dependent on another parameter that is a feature class or table; the field parameter will present a drop-down list of attribute fields from the dependent parameter.


You can save a layer file with a defined symbology and use that layer file as a template for how your model outputs should be symbolized when added to a map. This can be accomplished in two ways:

  • Set the Symbology of an output parameter to a layer file path like C:\Data\LandUseOverlay\Symbolized.lyrx in the Parameters tab of the tool Properties window.
  • Add the Apply Symbology From Layer tool to the end of your model, and set the Symbology Layer parameter to a layer file path.