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title: "Step Three: Create the Field Mapping File"
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locale: en-us
portal_url: https://docs.salesforce.com/developer/current/en-us/platform/data-loader-impl/guides/data-loader/command-line-create-mapping-file.md
canonical_url: https://developer.salesforce.com/docs/platform/data-loader-impl/guide/command-line-create-mapping-file.html
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  - Data Loader Guide
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---

# Step Three: Create the Field Mapping File

In this step, you create a mapping file with an .sdl file extension. In each line of the mapping file, pair a data source with its destination.

**note:** The Data Loader command-line interface is supported for Windows only.

-   Copy the following to a text file and save it with a name of accountInsertMap.sdl. This code is a data insert, so the data source is on the left of the equals sign and the destination field is on the right.

    <!-- otherprops: set_clipboard -->
    ```xml
    #Mapping values
                  #Thu May 26 16:19:33 GMT 2011
                  Name=Name
                  NumberOfEmployees=NumberOfEmployees
                  Industry=Industry
                
    ```

    For complex mappings, you can use the Data Loader user interface to map source and destination fields and then save those mappings to an .sdl file. It’s done on the Mapping dialog box by clicking **Save Mapping**.


**See Also**  


-   [Data Loader Command Line Introduction](https://developer.salesforce.com/docs/platform/data-loader-impl/guide/command-line-intro.md)
-   [Step Four: Create the Configuration File](https://developer.salesforce.com/docs/platform/data-loader-impl/guide/command-line-create-config-file.md)