Variable types in variable libraries

A variable library in Microsoft Fabric is a specialized item that centralizes the definition and management of variables, enabling scalable and automated configuration across workspaces and items.

Variables within a variable library can be a basic or advanced types, and each variable is uniquely identified by its name within the library item.

• Basic variable types in the Variable Library include simple, data types such as Boolean, DateTime (in ISO 8601 UTC format), Guid, Integer, Number, and String. These are straightforward values that can be directly assigned and used across different stages and environments.
• Advanced variable types are designed for more sophisticated use cases, such as referencing internal Fabric items or external connections. These include "item reference" types which store workspace and item IDs to point to specific Fabric items.

Supported types in variable libraries

Variables within a variable library have the following supported variable types

TypeType	Category	Description
Boolean	Basic	Represents true/false values.
Integer	Basic	Whole numbers without decimals.
Number	Basic	Numeric values, including decimals.
String	Basic	Text values or sequences of characters.
DateTime	Basic	Date and time represented as the ISO 8601 standard yyyy-MM-ddTHH:mm:ss.xxxZ, where: yyyy-MM-dd is the four-digit year, followed by the two-digit month and two-digit day. T separates the date and the time. HH:mm:ss.xxx is the two-digit hour in 24-hour format, followed by the two-digit minute, two-digit second, and three-digit millisecond. Z indicates that the time is in Coordinated Universal Time (UTC).
Guid	Basic	Globally unique identifier used for distinct object identification.
Item reference	Advanced	Used within the Fabric Variable Library to hold a reference to an existing Fabric item—such as a lakehouse, notebook, or data pipeline, by storing its workspace ID and item ID.

Variable properties

Each variable in the variable library has the following properties:

Property	Description
Name	The unique identifier for the variable. Used to reference the variable in scripts or workflows.
Note (optional)	A descriptive comment or annotation about the variable. Can include context, usage notes, or special instructions. Maximum length: 2,048 characters.
Type	Defines the data type of the variable (e.g., string, integer, boolean, array). Determines how the value is interpreted and validated.
Default value set	The initial value assigned to the variable when no other value is provided. Ensures consistent behavior in workflows. The default value set cannot be renamed.
Alternative value sets (optional)	Additional predefined sets of values that can be applied under specific conditions or scenarios. Useful for environment-specific configurations or fallback options.

Naming conventions

Variable name

The name of a variable inside the variable library must follow these conventions:

• Isn't empty
• Doesn't have leading or trailing spaces
• Starts with a letter or an underscore
• Can include letters, numbers, underscores, and hyphens
• Doesn't exceed 256 characters in length

The variable name is not case sensitive.

After a variable has a defined value, if you try to change its type, a consent dialog appears. The dialog alerts you that all the variable values will be reset and that this change could be a breaking change on the consumer item side.

Considerations and limitations

Size limitations

• There can be up to 1,000 variables and up to 1,000 value sets, as long as you meet both of these requirements:

  • The total number of cells in the alternative value sets is less than 10,000.
  • The item's size doesn't exceed 1 MB.

  These requirements are validated when you save changes.

• The note field can have up to 2,048 characters.

• The value-set description field can have up to 2,048 characters.