Flow variables

  • Release version: Zurich
  • Updated September 19, 2025
  • 2 minutes to read
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    Summary of Flow variables

    Flow variables in ServiceNow enable you to create and modify variables accessible throughout the entire flow. They function similarly to Workflow scratchpad variables and are available as data pills in the Data panel, allowing you to set and retrieve values dynamically during flow execution. Unlike subflow inputs and outputs, which are limited to the start and end of subflows, flow variables maintain accessibility throughout the flow's lifecycle.

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    Creating and Using Flow Variables

    You create flow variables via the Flow Variables option in the More Actions menu, allowing multiple variables to be defined simultaneously with specified names and data types. These variables then appear as data pills in the Flow Variables section of the Data panel.

    To assign or update values, use the Set Flow Variables flow logic, which takes the variable name and the data value as inputs. Values assigned to flow variables are mutable and can be changed at any time during the flow. If a variable is not assigned a value, its default is null.

    When assigning multiple variables, the order matters because variables can reference earlier variables or other data pills. The last assigned value for any repeated variable assignment is the one used at runtime. Maintaining the correct order ensures proper referencing and prevents unintended null values.

    Execution and Data Types

    During flow execution, the Set Flow Variables action provides detailed information in the execution details pane, displaying variable names, types, configurations, and runtime values. This transparency helps track variable state and usage throughout the flow.

    Supported data types for flow variables include:

    • Array.Object
    • Date/Time
    • Decimal
    • Floating-point number
    • Integer
    • JSON Object
    • Reference
    • String
    • True/False

    Practical Implications for ServiceNow Customers

    Using flow variables enhances your ability to manage data flexibly across different steps of a flow without the constraints of subflow boundaries. This capability allows for more dynamic and maintainable flow designs, enabling you to track and manipulate state information efficiently throughout process execution.

    By leveraging flow variables and the Set Flow Variables logic, you can create complex flows that adapt based on intermediate data, improving automation accuracy and responsiveness.

    Similar to Workflow scratchpad variables, create variables that you can use and modify directly in your flow. Access flow variables as data pills directly in the Data panel.

    Use flow variables to set and retrieve values throughout a flow. Flow variables are similar to subflow inputs and outputs. Both define data available to a flow or subflow. The main difference between them is when they are accessible. Flow variables are accessible throughout a flow. Inputs are only accessible at the start of a subflow, and outputs are only accessible when a subflow completes.

    Creating flow variables

    Create variables with the Flow Variables option on the More Actions menu. You can create several variables at a time by choosing a name and data type for each one. Flow variables appear as data pills in the Flow Variables section of the Data panel.

    Assigning values to flow variables

    Assign values to variables with the Set Flow Variables flow logic. Set Flow Variables has the following inputs:
    • The name of the variable.
    • The data value for the variable.

    You can assign values to all of your variables with a single use of Set Flow Variables. Unlike other data pills, the values assigned to flow variables are mutable and can be changed at any time. Using Set Flow Variables overrides the current value of the variable. If no value is assigned to a variable, the default value is null.

    Flow variable values are set in the order in which they're assigned from top to bottom. If you set the value of the same variable multiple times, the flow only uses the last value set. For example, these three variable definitions result in the variable having the runtime value of last value set.

    Table 1. Last value set defines flow variable value
    Order Variable Configuration
    1 variable first value set
    2 variable second value set
    3 variable last value set

    Variable values can reference any data pill from earlier in the flow, including other variables. If you set variable values by reference to other data pills, you must maintain the order of the variable assignments. The referenced value must always come before the variable that uses the referenced value. Changing the order may produce null values. For example, these variable definitions only produce the expected runtime values when you maintain the order of the variable definitions.

    Table 2. Setting variable values by reference
    Order Variable Configuration Runtime Value
    1 variable1 One One
    2 variable2 {variable1}, Two One, Two
    3 variable3 {variable1}, {variable2}, Three One, Two, Three

    Flow execution details

    A summary of the Set Flow Variables flow logic appears in the execution details. The details show the name, type, configuration, and runtime values for all the variables set with the action. Execution details also provide information about the variables when they're used in actions or flow logic. In that case, it shows the type, configuration, and runtime values.

    Supported data types

    Workflow Studio supports the following data types for flow variables:
    • Array.Object
    • Date/Time
    • Decimal
    • Floating-point number
    • Integer
    • JSON
    • Object
    • Reference
    • String
    • True/False