• Avoid periods, ellipses, and dynamic metadata field names.

• Metadata field names must not contain a dot. For example, use of the following field name would return a Bad Request (400) error:

  {
      "preference.color": "pink"
  }
  

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  One way of handling this limitation is to nest attributes:

  {
      "preference": {
          "color": "pink"
      }
  }
  

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• Alternately, you can use any delimiter that is not . or $. However, you can the . delimiter in the data values such as in the below example:

  {
      "preference": "light.blue"
  }
  

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• Do not use dynamic field names. For example, instead of using the following structure:

  "participants": {
      "Alice" : {
          "role": "sender"
      },
      "Bob" : {
          "role": "receiver"
      }
  }
  

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  Use this:

  "participants": [
      {
          "name": "Alice",
          "role": "sender"
      },
      {
          "name" : "Bob",
          "role": "receiver"
      }
  ]
  

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Use a consistent data type each time you create or update a given metadata field. For example, if you use user.user_metadata.age = "23" for one user and user.user_metadata.age = 23 for another user, it will cause issues when retrieving the data.

• Both app_metadata and user_metadata are limited to a size of 16 MB each. Metadata storage is not designed to be a general purpose data store, and you should still use your own external storage facility when possible. When using Rules and/or the Management Dashboard, your metadata limits may be lower.

• When setting the user_metadata field using the Authentication API's Signup endpoint, you are limited to a maximum of 10 String fields and 500 characters. For an example of working with metadata during a custom signup process, see Custom Signup > Using the API.

Store any information that you want use to customize Auth0 emails in metadata and preferably user_metadata if the user is allowed to change it, such as information used to determine the language for an email.

The app_metadata field should not contain any of these properties:

• __tenant
• _id
• blocked
• clientID
• created_at
• email_verified
• email
• globalClientID
• global_client_id
• identities
• lastIP
• lastLogin
• loginsCount
• metadata
• multifactor_last_modified
• multifactor
• updated_at
• user_id

• Metadata
• Manage User Metadata
• Update Metadata with the Management API
• User Metadata in Rules
• User Data Storage Best Practices