> ## Documentation Index > Fetch the complete documentation index at: https://stytch.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # External IDs > Assign and use external IDs for Stytch resources in place of Stytch-assigned UUIDs. export const organization = "Represents an instance or tenant in your application, typically mapping to each of your top-level customers."; export const member = "Represents an individual end user's account within a given Organization, uniquely identified within that Organization by their email address."; export const userTip = "Represents an end user's account in your application."; When a User is created in Stytch, they will be assigned a unique identifier that looks like a UUID. For your convenience, you may choose to additionally assign an "external ID" to a user which can then be used in any place where the Stytch `user_id` is expected. ## Assigning an external ID at creation When calling the [Create User](/api-reference/consumer/api/users/create-user) endpoint, you may pass in an optional `external_id` parameter. The `external_id` is a string consisting of alphanumeric, ., `_`, or `-` characters with a maximum length of 128 characters. External IDs must be unique across users in your project. You may also set an external ID during a call to the [Migrate Password](/api-reference/consumer/api/passwords/migrate) endpoint, but only if the user does not yet exist and is created. If the user already exists, you must use the [Update User](/api-reference/consumer/api/users/update-user) endpoint to assign or reassign the `external_id`. ## Assigning an external ID later If a user has already been created, you may assign it an `external_id` *later* with the [Update User](/api-reference/consumer/api/users/update-user) endpoint. Similar to creation, pass in an `external_id` parameter and it will then be assigned to that user. Again, remember that external IDs must be unique within your project. ## Updating a user's external ID If you wish to change a user's external ID, you may use the same [Update User](/api-reference/consumer/api/users/update-user) endpoint listed above. After this point, you will no longer be able to refer to that user by its *old* `external_id`. ## Using external IDs In any endpoint that expects a `user_id`, you may instead choose to pass in your custom-defined `external_id`. For clarity, all responses *from* Stytch will continue to use the Stytch-defined `user_id`, though `external_id` will exist as a subfield within the User object. When a Member or Organization is created in Stytch, they will be assigned a unique identifier that looks like a UUID. For your convenience, you may choose to additionally assign an "external ID" to a member which can then be used in any place where the Stytch `member_id` is expected. You can also assign an "organization external ID" to an organization which can then be used any place where the Stytch `organization_id` is expected. ## Assigning an external ID at creation An External IDs is a string consisting of alphanumeric, `.`, `_`, or `-` characters with a maximum length of 128 characters. Member external IDs must be unique across members in a given organization, but may be reused across different organizations in the same project. Organization external IDs must be unique across all organizations in the same project When calling the [Create Member](/api-reference/b2b/api/members/create-member) you may pass in an optional `external_id` parameter. When calling the [Create Organization](/api-reference/b2b/api/organizations/create-organization) you may pass in an optional `organization_external_id` parameter. You may also set an external ID during a call to the [Migrate Password](/api-reference/b2b/api/passwords/migrate) endpoint, but only if the member does not yet exist and is created. If the member already exists, you must use the [Update Member](/api-reference/b2b/api/members/update-member) endpoint to assign or reassign the `external_id`. ## Assigning an external ID later If a member has already been created, you may assign it an `external_id` *later* with the [Update Member](/api-reference/b2b/api/members/update-member) endpoint. Similar to creation, pass in an `external_id` parameter and it will then be assigned to that member. Again, remember that external IDs must be unique within a given organization, but may be reused across different organizations in the same project. Organizations can similarly be assigned an `organization_external_id` later with the [Update Organization](/api-reference/b2b/api/organizations/update-organization) endpoint. ## Updating external IDs If you wish to change a member's external ID you may use the same [Update Member](/api-reference/b2b/api/members/update-member) endpoints listed above. If you wish to change an organization's external ID you may use the [Update Organization](/api-reference/b2b/api/organizations/update-organization) endpoint. After this point, you will no longer be able to refer to that entity by its *old* `external_id`. ## Using external IDs In any endpoint that expects a `member_id`, you may instead choose to pass in your custom-defined `external_id`. For clarity, all responses *from* Stytch will continue to use the Stytch-defined `member_id`, though `external_id` will exist as a subfield within the Member object. In any endpoint that expects an `organization_id`, you may instead choose to pass in your custom-defined `organization_external_id`. Similarly, all responses *from* Stytch will continue to use the Stytch-defined `organization_id`, though `organization_external_id` will exist as a subfield within the Organization object. ```js theme={null} const stytch = require('stytch'); const client = new stytch.B2BClient({ project_id: '${projectId}', secret: '${secret}', }); const params = { organization_id: "example-organization-external-id", member_id: "example-member-external-id", }; client.organizations.members.get(params) .then(resp => { console.log(resp) }) .catch(err => { console.log(err) }); ```