A Global field is a reusable group of fields. Define it once and use it across multiple content types in your stack. This helps you avoid recreating the same set of fields repeatedly.
You can update the following properties of a Global field at any time:
Note: You can now show a Global field as a separate tab in the entry editor for better organization and navigation. Learn how to enable the Show as Tab option.
For example, to standardize SEO metadata across all pages, you can create a Global field named SEO and add subfields such as:
Once created, add the SEO Global field to all relevant content types. When content creators add entries, the SEO field appears automatically with the predefined subfields (Meta Title, Meta Description, Meta Keywords, and an Enable Search Indexing toggle), ready to use, as shown below:

Note: Updating fields in an existing content type may result in data loss. Before making changes, refer to the Content Type Change Management documentation.
Content managers can copy the values of an instance within a Global field and paste them into:
This simplifies content duplication and speeds up entry creation.
To copy and paste field values across group fields, log in to your Contentstack account and perform the following steps:
Note: The destination instance must match the original instance’s name and structure.

Additional Resources: