Salesforce Platform Developer Practice Exam 2026 – All-in-One Guide to Ace Your Certification!

External IDs are custom fields that can be used to reference records from external data sources, making data integration easier. The primary types of custom fields that can serve as external IDs in Salesforce are text, number, and email fields. This flexibility allows for a variety of integrations with external systems where one might want to map Salesforce records to records in other applications, or retrieve specific records using unique identifiers from those systems.

Text and number fields are often used as external IDs because they can uniquely identify records without requiring complex data types or manipulations. Email fields may serve similar functions where email addresses work as unique identifiers, making them suitable for external references as well.

The other types of fields mentioned, such as date and time fields or formula fields, do not qualify for use as external IDs. Date and time fields lack the uniqueness required for external references, and formula fields are dynamically calculated values which can change based on underlying data conditions, making them unsuitable as static identifiers. Additionally, the option mentioning custom objects only is misleading, as external IDs apply to fields within standard or custom objects, not limited to custom objects alone.