TFS 2017 | Team Services
Use a variable group to store values that you want to make available across multiple build and release definitions. Variable groups are defined and managed in the Library tab of the Build & Release hub.
Variable groups can only be used in release definitions in TFS 2017 and Team Services at present. They cannot yet be used in build definitions.
To use a variable group in a release definition, open the definition, select the Variables tab, and then choose Link variable group(s). When a variable group is linked to a release definition, all the variables in the group are available for use in all environments of that definition.
You cannot link a variable group to a specific environment in a release definition at present.
Any changes made centrally to a variable group, such as a change in the value of a variable or the addition of new variables, will automatically be made available to all the release definitions in which the variable group is used.
Variable groups follow the library security model.