A hard ID is a stable, explicit identifier that reliably points to one person or account, such as an email address, phone number, customer ID, or login. A soft ID is a weaker signal that suggests identity but can be shared, reset, or expire, such as a cookie, device ID, or IP address.
Category
Identity
Also known as
hard ID; soft ID; hard identifier; soft identifier
Identity resolution is largely the work of stitching behavior collected under soft IDs to a hard ID once the person logs in, subscribes, identifies, or buys. Until that link is made, the activity is effectively anonymous.
In practice
Design tracking so a hard ID is captured as early as it is legitimately available, then connect the earlier soft-ID behavior to it. Personalization and consent both depend on knowing which real person or account a soft ID belongs to. For how this plays out in Bloomreach specifically, seeSoft IDs and Hard IDs in Bloomreach Engagement.