Validation

Validation ensures users enter correct data before form submission. Espanso Dynamic Forms uses JSON Schema validation powered by AJV.

How Validation Works

Define validation rules in your schema. The form automatically:

1. Validates input as users type
2. Shows error messages for invalid fields
3. Prevents submission until all fields are valid

Required Fields

Mark fields that must be filled:

schema:
  type: object
  properties:
    name:
      type: string
    email:
      type: string
  required:
    - name
    - email

Required Array

The required array is at the same level as properties, not inside individual field definitions.

String Validation

Minimum and Maximum Length

username:
  type: string
  minLength: 3
  maxLength: 20

Pattern (Regular Expression)

email:
  type: string
  pattern: "^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$"

Format

Some common formats are built-in:

email:
  type: string
  format: email

website:
  type: string
  format: uri

birthdate:
  type: string
  format: date

Format	Validates
email	Email address
uri	URL
date	Date (YYYY-MM-DD)
time	Time (HH:MM:SS)
date-time	ISO 8601 datetime

Number Validation

Minimum and Maximum

age:
  type: integer
  minimum: 0
  maximum: 120

Exclusive Bounds

rating:
  type: number
  exclusiveMinimum: 0    # Must be > 0, not >= 0
  exclusiveMaximum: 10   # Must be < 10, not <= 10

Multiple Of

quantity:
  type: integer
  multipleOf: 5   # Must be 5, 10, 15, etc.

Array Validation

Minimum and Maximum Items

tags:
  type: array
  items:
    type: string
  minItems: 1
  maxItems: 10

Unique Items

Prevent duplicate selections:

selections:
  type: array
  items:
    type: string
    enum:
      - Option A
      - Option B
      - Option C
  uniqueItems: true

Enum Validation

Restrict to specific values:

priority:
  type: string
  enum:
    - High
    - Medium
    - Low

Complete Validation Example

schema:
  type: object
  properties:
    username:
      type: string
      minLength: 3
      maxLength: 20
    email:
      type: string
      format: email
    password:
      type: string
      minLength: 8
    age:
      type: integer
      minimum: 13
      maximum: 120
    website:
      type: string
      format: uri
    interests:
      type: array
      items:
        type: string
        enum:
          - Technology
          - Sports
          - Music
          - Art
          - Science
      minItems: 1
      maxItems: 3
      uniqueItems: true
    agreedToTerms:
      type: boolean
      const: true   # Must be true to submit
  required:
    - username
    - email
    - password
    - agreedToTerms

Validation Keywords Reference

String Keywords

Keyword	Description	Example
minLength	Minimum character count	minLength: 3
maxLength	Maximum character count	maxLength: 100
pattern	Regex pattern	pattern: "^[A-Z]"
format	Built-in format	format: email

Number Keywords

Keyword	Description	Example
minimum	Minimum value (inclusive)	minimum: 0
maximum	Maximum value (inclusive)	maximum: 100
exclusiveMinimum	Minimum value (exclusive)	exclusiveMinimum: 0
exclusiveMaximum	Maximum value (exclusive)	exclusiveMaximum: 100
multipleOf	Must be divisible by	multipleOf: 5

Array Keywords

Keyword	Description	Example
minItems	Minimum array length	minItems: 1
maxItems	Maximum array length	maxItems: 10
uniqueItems	No duplicates allowed	uniqueItems: true

General Keywords

Keyword	Description	Example
enum	Allowed values	enum: [A, B, C]
const	Must equal this value	const: true
default	Default value	default: "Hello"

Validation Behavior

Real-Time Validation

Fields are validated as users type. Error messages appear below invalid fields.

Submit Validation

The form cannot be submitted while validation errors exist.

Optional Fields

Fields not in the required array are optional. They're only validated if the user enters a value.