Global fields are reusable field sets defined once and used across content types, simplifying modeling, ensuring consistency, and avoiding field recreation.
For example, let's say you need to store employee addresses across different content types, such as Employee Profiles and Office Locations. Instead of adding the same set of address fields manually each time, you can create an Address Global field and reuse it across multiple content types.
Additionally, Nested Global fields allow you to include a Global field within another Global field, making it easy to structure complex data relationships.
Note: When working with specific branches, any Global fields you create or update will be unique to that branch. Refer to the Branch-specific Modules documentation for more details.
To create a Global field, log in to your Contentstack account, and perform the following steps:
Tip: Refer to the Restricted Keywords for Unique IDs to avoid using reserved keywords.
Tip: To modify field behavior, click the Properties icon displayed next to each field and configure its settings.
Your Address Global field will look as follows:

If you have multiple reusable components within a content model, you can use Nested Global fields. For example, if you have an Employee Details Global field that requires an address section, you can nest the Address Global field inside it instead of recreating the same fields.
To add a nested Global field, log in to your Contentstack account, and perform the following steps:

Nested Global fields help in maintaining consistency and reducing redundancy in complex content structures.
To create a Global field via API, refer to the Create Global Field API request.