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Entities are custom data structures you define to store information in your Base44 applications. They work like database tables, with built-in validation, real-time updates, and security rules. Use the entities module to work with entity data in code.
To configure security rules for your entity, see Security.

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Define entity schemas

Entities are defined using a JSON Schema that describes the data structure and validation rules.

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Basic schema structure

Here’s an entity schema template: 
{
  "name": "my_entity",
  "type": "object",
  "title": "My Entity",
  "description": "Description of what this entity represents",
  "properties": {
    "<field_name>": {
      "type": "<field_type>",
      "<option>": "<value>"
    }
  },
  "required": ["<field_name>"]
}

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Schema fields

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name
string
String identifier for the entity.
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type
string
required
Must be "object".
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title
string
User-friendly display name.
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description
string
Description of what the entity represents.
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properties
object
required
Object containing your field definitions. Each field has a type and optional validation rules.

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Field types

Entities support various field types to define different kinds of data you can store: string, integer, number, boolean, array, and object. Each field inside properties requires a type. Based on the type, you can add validation options.

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String fields

String fields support these options:
  • minLength / maxLength: Control minimum and maximum character count.
  • pattern: Regular expression for custom validation.
  • format: Predefined formats. Supported values:
    • "date"
    • "date-time"
    • "time"
    • "email"
    • "uri"
    • "hostname"
    • "ipv4"
    • "ipv6"
    • "uuid"
  • enum: Restrict to specific allowed values. Define as an array: ["value1", "value2", "value3"].
  • default: Default value if none provided.

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Integer fields

Integer fields support these options:
  • minimum / maximum: Set inclusive lower/upper bounds.
  • default: Default value if none provided.

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Number fields

Number fields support these options:
  • minimum / maximum: Set inclusive lower/upper bounds.
  • default: Default value if none provided.

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Boolean fields

Boolean fields support these options:
  • default: Default value if none provided.

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Array fields

Array fields support these options:
  • items: Define the type/schema for array elements.
  • default: Default array value if none provided.

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Object fields

Object fields support these options:
  • properties: Define the fields within the object.
  • required: List of required property names.

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Required fields

Specify which fields must be provided: 
{
  "required": ["title", "email"]
}

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Complete example

Here’s a complete entity schema: 
{
  "name": "Task",
  "type": "object",
  "title": "Task",
  "description": "A task item with priority, due date, and completion status",
  "properties": {
    "title": {
      "type": "string",
      "minLength": 1,
      "maxLength": 200
    },
    "description": {
      "type": "string",
      "maxLength": 1000
    },
    "priority": {
      "type": "string",
      "enum": ["low", "medium", "high"],
      "default": "medium"
    },
    "completed": {
      "type": "boolean",
      "default": false
    },
    "due_date": {
      "type": "string",
      "format": "date"
    },
    "tags": {
      "type": "array",
      "items": {"type": "string"}
    }
  },
  "required": ["title"]
}

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Viewing schemas in dashboard

You can view your entity schemas directly in the Base44 dashboard:
  1. Go to your app’s Data section.
  2. Select the entity you want to view.
  3. Click Schema to view the current JSON schema.

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See also