---
title: Entity Reference fields
description: A reusable set of identifier fields used to reference other entities in relationship contexts. Each field holds a keyword array of identifiers following...
url: https://www.elastic.co/elastic/docs-builder/docs/3369/reference/ecs/ecs-entity_reference
products:
  - Elastic Common Schema (ECS)
applies_to:
  - Elastic Cloud Serverless: Generally available
  - Elastic Stack: Generally available
---

# Entity Reference fields
A reusable set of identifier fields used to reference other entities in relationship contexts. Each field holds a keyword array of identifiers following the same conventions as the corresponding ECS root field. Only the fields defined in this field set might appear, ad-hoc or integration-specific property names are not allowed.
<warning>
  This field set is alpha and subject to change.
</warning>


## Entity Reference field details


| Field                                                                 | Description                                                                                                                                                                              | Level    |
|-----------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|
| [entity_reference.entity.id](#field-entity-reference-entity-id)       | Identifiers of referenced entities, using the same meaning as root `entity.id` (stable id for correlation within scope).type: keywordNote: This field should contain an array of values. | extended |
| [entity_reference.host.id](#field-entity-reference-host-id)           | Referenced host ids.type: keywordNote: This field should contain an array of values.                                                                                                     | extended |
| [entity_reference.host.name](#field-entity-reference-host-name)       | Referenced host names.type: keywordNote: This field should contain an array of values.                                                                                                   | extended |
| [entity_reference.service.id](#field-entity-reference-service-id)     | Referenced service ids.type: keywordNote: This field should contain an array of values.                                                                                                  | extended |
| [entity_reference.service.name](#field-entity-reference-service-name) | Referenced service names.type: keywordNote: This field should contain an array of values.                                                                                                | extended |
| [entity_reference.user.domain](#field-entity-reference-user-domain)   | Referenced user directory or AD/LDAP domain names (same semantics as ECS `user.domain`).type: keywordNote: This field should contain an array of values.                                 | extended |
| [entity_reference.user.email](#field-entity-reference-user-email)     | Referenced user email addresses.type: keywordNote: This field should contain an array of values.                                                                                         | extended |
| [entity_reference.user.id](#field-entity-reference-user-id)           | Referenced user ids.type: keywordNote: This field should contain an array of values.                                                                                                     | extended |
| [entity_reference.user.name](#field-entity-reference-user-name)       | Referenced user short names or logins.type: keywordNote: This field should contain an array of values.                                                                                   | extended |


## Field reuse

The `entity_reference` fields are expected to be nested at:
- `entity.relationships.administers`
- `entity.relationships.depends_on`
- `entity.relationships.owns`
- `entity.relationships.supervises`

Note also that the `entity_reference` fields are not expected to be used directly at the root of the events.