The Unique property ensures that the value of a field does not repeat across entries within the same content type. It helps maintain data integrity by preventing duplicate values.
When you mark a field as Unique in a content type, Contentstack enforces the following rules:

Note:
When you copy an entry that includes fields marked as Unique, Contentstack automatically appends a timestamp to those field values. This prevents conflicts and ensures the copied entry can be saved successfully.
This applies to:
Example:
If a Unique field originally contains: promo-code
After copying, it becomes: promo-code – Copy (2025-01-10 14:22:18)

This adjustment ensures that the copied entry remains valid and does not trigger a uniqueness error during the save process.
The Unique property helps maintain data accuracy by preventing duplicate values within a content type. By automatically handling Unique fields during entry duplication, Contentstack streamlines content creation while preserving data integrity. Use this feature to ensure your content model supports reliable, conflict-free data entry across all locales and workflows.