externalid

External ID, short for external identifier, is an identifier used by external systems to reference a record in another system. It is separate from the internal identifiers assigned by the receiving system, and it serves as a stable linkage point for data exchange, synchronization, and integration.

The primary purpose of an external ID is to enable upsert and deduplication operations. When data is imported, the system can use the external ID to locate an existing record: if a match is found, the record is updated; if not, a new record is created. This approach helps keep records in sync across disparate systems and reduces the risk of creating duplicates.

External IDs can take various forms, including text strings, numbers, or GUIDs. The choice depends on the source system and the requirements of the integration. In many implementations, external IDs are defined as a dedicated field in a data object or record type. Some systems allow explicit constraints, such as making the external ID field unique or indexed to improve lookup performance.

Common considerations include ensuring the external ID is stable over time, avoiding sensitive information, and maintaining data quality across systems. Changes to external IDs can break mappings, so identifiers are typically treated as immutable once created.

Salesforce, for example, supports External ID fields of types such as Text, Number, or Email, with options to enforce uniqueness for reliable upsert operations. In API and ETL workflows, external IDs appear as key fields in payloads to link and synchronize records across services.

See also: upsert, data mapping, deduplication, data integration.