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TanStack Form provides flexible validation with support for synchronous and asynchronous validation, field-level and form-level rules, and schema-based validation.

​
Validation Timing

Control when validation runs by choosing the appropriate callback:
  • onChange - Validates on every keystroke
  • onBlur - Validates when the field loses focus
  • onSubmit - Validates when the form is submitted
  • onMount - Validates when the field mounts
Each has an async counterpart: onChangeAsync, onBlurAsync, etc.

​
On Change Validation

Validate on every keystroke: 
import { Component } from '@angular/core'
import { TanStackField, injectForm } from '@tanstack/angular-form'
import type { FieldValidateFn } from '@tanstack/angular-form'

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <ng-container
      [tanstackField]="form"
      name="age"
      [validators]="{
        onChange: ageValidator
      }"
      #age="field"
    >
      <label [for]="age.api.name">Age:</label>
      <input
        [id]="age.api.name"
        [name]="age.api.name"
        [value]="age.api.state.value"
        type="number"
        (input)="age.api.handleChange($any($event).target.valueAsNumber)"
      />
      @if (age.api.state.meta.errors) {
        <em role="alert">{{ age.api.state.meta.errors.join(', ') }}</em>
      }
    </ng-container>
  `,
})
export class AppComponent {
  ageValidator: FieldValidateFn<any, any, any, any, number> = ({ value }) =>
    value < 13 ? 'You must be 13 to make an account' : undefined

  form = injectForm({
    defaultValues: {
      age: 0,
    },
    onSubmit({ value }) {
      console.log(value)
    },
  })
}

​
On Blur Validation

Validate when the field loses focus: 
@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <ng-container
      [tanstackField]="form"
      name="age"
      [validators]="{
        onBlur: ageValidator
      }"
      #age="field"
    >
      <label [for]="age.api.name">Age:</label>
      <input
        [id]="age.api.name"
        [name]="age.api.name"
        [value]="age.api.state.value"
        type="number"
        (blur)="age.api.handleBlur()"
        (input)="age.api.handleChange($any($event).target.valueAsNumber)"
      />
      @if (age.api.state.meta.errors) {
        <em role="alert">{{ age.api.state.meta.errors.join(', ') }}</em>
      }
    </ng-container>
  `,
})
export class AppComponent {
  ageValidator: FieldValidateFn<any, any, any, any, number> = ({ value }) =>
    value < 13 ? 'You must be 13 to make an account' : undefined

  // ...
}

​
Multiple Validators

Combine multiple validators at different times: 
@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <ng-container
      [tanstackField]="form"
      name="age"
      [validators]="{
        onChange: ageValidator,
        onBlur: minimumAgeValidator
      }"
      #age="field"
    >
      <label [for]="age.api.name">Age:</label>
      <input
        [id]="age.api.name"
        [name]="age.api.name"
        [value]="age.api.state.value"
        type="number"
        (blur)="age.api.handleBlur()"
        (input)="age.api.handleChange($any($event).target.valueAsNumber)"
      />
      @if (!age.api.state.meta.isValid) {
        <em role="alert">{{ age.api.state.meta.errors.join(', ') }}</em>
      }
    </ng-container>
  `,
})
export class AppComponent {
  ageValidator: FieldValidateFn<any, any, any, any, number> = ({ value }) =>
    value < 13 ? 'You must be 13 to make an account' : undefined

  minimumAgeValidator: FieldValidateFn<any, any, any, any, number> = ({ value }) =>
    value < 0 ? 'Invalid value' : undefined

  // ...
}

​
Displaying Errors

​
Error Array

Display all errors from the errors array: 
@if (age.api.state.meta.errors) {
  <em role="alert">{{ age.api.state.meta.errors.join(', ') }}</em>
}

​
Error Map

Access specific errors by validation timing using errorMap: 
@if (age.api.state.meta.errorMap['onChange']) {
  <em role="alert">{{ age.api.state.meta.errorMap['onChange'] }}</em>
}

​
Typed Errors

Return typed error objects for more control: 
ageValidator: FieldValidateFn<any, any, any, any, number> = ({ value }) =>
  value < 13 ? { isOldEnough: false } : undefined
Then check specific error properties: 
@if (!age.api.state.meta.errorMap['onChange']?.isOldEnough) {
  <em role="alert">The user is not old enough</em>
}

​
Form-Level Validation

Define validation at the form level instead of per-field: 
import { Component } from '@angular/core'
import { TanStackField, injectForm, injectStore } from '@tanstack/angular-form'

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <div>
      <ng-container [tanstackField]="form" name="age" #age="field">
        <!-- ... -->
        @if (formErrorMap().onChange) {
          <div>
            <em>There was an error on the form: {{ formErrorMap().onChange }}</em>
          </div>
        }
      </ng-container>
    </div>
  `,
})
export class AppComponent {
  form = injectForm({
    defaultValues: {
      age: 0,
    },
    onSubmit({ value }) {
      console.log(value)
    },
    validators: {
      // Add validators to the form the same way you would add them to a field
      onChange({ value }) {
        if (value.age < 13) {
          return 'Must be 13 or older to sign'
        }
        return undefined
      },
    },
  })

  // Subscribe to the form's error map so that updates to it will render
  formErrorMap = injectStore(this.form, (state) => state.errorMap)
}

​
Setting Field Errors from Form Validators

Set field-level errors from form validators, useful for server-side validation: 
import { Component } from '@angular/core'
import { TanStackField, injectForm } from '@tanstack/angular-form'

@Component({
  selector: 'app-root',
  imports: [TanStackField],
  template: `
    <form (submit)="handleSubmit($event)">
      <div>
        <ng-container
          [tanstackField]="form"
          name="age"
          #ageField="field"
        >
          <label [for]="ageField.api.name">Age:</label>
          <input
            type="number"
            [name]="ageField.api.name"
            [value]="ageField.api.state.value"
            (blur)="ageField.api.handleBlur()"
            (input)="ageField.api.handleChange($any($event).target.valueAsNumber)"
          />
          @if (ageField.api.state.meta.errors.length > 0) {
            <em role="alert">{{ ageField.api.state.meta.errors.join(', ') }}</em>
          }
        </ng-container>
      </div>
      <button type="submit">Submit</button>
    </form>
  `,
})
export class AppComponent {
  form = injectForm({
    defaultValues: {
      age: 0,
      socials: [],
      details: {
        email: '',
      },
    },
    validators: {
      onSubmitAsync: async ({ value }) => {
        // Validate the value on the server
        const hasErrors = await verifyDataOnServer(value)
        if (hasErrors) {
          return {
            form: 'Invalid data', // The `form` key is optional
            fields: {
              age: 'Must be 13 or older to sign',
              // Set errors on nested fields with the field's name
              'socials[0].url': 'The provided URL does not exist',
              'details.email': 'An email is required',
            },
          }
        }

        return null
      },
    },
  })

  handleSubmit(event: SubmitEvent) {
    event.preventDefault()
    event.stopPropagation()
    this.form.handleSubmit()
  }
}
Field-level validators override form-level field errors. If both return errors for the same field, only the field-level error is shown.

​
Asynchronous Validation

Use async validators for network requests or other async operations: 
import { Component } from '@angular/core'
import { TanStackField, injectForm } from '@tanstack/angular-form'
import type { FieldValidateAsyncFn } from '@tanstack/angular-form'

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <ng-container
      [tanstackField]="form"
      name="age"
      [validators]="{ onChangeAsync: ageValidator }"
      #age="field"
    >
      <label [for]="age.api.name">Age:</label>
      <input
        [id]="age.api.name"
        [name]="age.api.name"
        [value]="age.api.state.value"
        type="number"
        (input)="age.api.handleChange($any($event).target.valueAsNumber)"
      />
      @if (age.api.state.meta.errors) {
        <em role="alert">{{ age.api.state.meta.errors.join(', ') }}</em>
      }
    </ng-container>
  `,
})
export class AppComponent {
  ageValidator: FieldValidateAsyncFn<any, string, number> = async ({ value }) => {
    await new Promise((resolve) => setTimeout(resolve, 1000))
    return value < 13 ? 'You must be 13 to make an account' : undefined
  }

  form = injectForm({
    defaultValues: {
      age: 0,
    },
    onSubmit({ value }) {
      console.log(value)
    },
  })
}

​
Combining Sync and Async Validation

Run synchronous validation first, then async validation: 
@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <ng-container
      [tanstackField]="form"
      name="age"
      [validators]="{ onBlur: ensureAge13, onBlurAsync: ensureOlderAge }"
      #age="field"
    >
      <label [for]="age.api.name">Age:</label>
      <input
        [id]="age.api.name"
        [name]="age.api.name"
        [value]="age.api.state.value"
        type="number"
        (blur)="age.api.handleBlur()"
        (input)="age.api.handleChange($any($event).target.value)"
      />
      @if (age.api.state.meta.errors) {
        <em role="alert">{{ age.api.state.meta.errors.join(', ') }}</em>
      }
    </ng-container>
  `,
})
export class AppComponent {
  ensureAge13: FieldValidateFn<any, any, any, any, number> = ({ value }) =>
    value < 13 ? 'You must be at least 13' : undefined

  ensureOlderAge: FieldValidateAsyncFn<any, string, number> = async ({ value }) => {
    const currentAge = await fetchCurrentAgeOnProfile()
    return value < currentAge ? 'You can only increase the age' : undefined
  }

  // ...
}
By default, async validators only run if sync validators pass. Set asyncAlways: true to always run async validators.

​
Built-in Debouncing

Debounce async validation to prevent excessive API calls: 
<ng-container
  [tanstackField]="form"
  name="age"
  [asyncDebounceMs]="500"
  [validators]="{ onChangeAsync: someValidator }"
  #age="field"
>
  <!-- ... -->
</ng-container>
Or set debounce per-validator: 
<ng-container
  [tanstackField]="form"
  name="age"
  [validators]="{
    onChangeAsyncDebounceMs: 1500,
    onChangeAsync: someValidator,
    onBlurAsync: otherValidator
  }"
  #age="field"
>
  <!-- ... -->
</ng-container>

​
Schema-Based Validation

Use schema libraries for concise, type-safe validation. TanStack Form supports the Standard Schema specification.

​
Supported Libraries

Use the latest versions of these libraries to ensure Standard Schema support.

​
Using Zod

import { Component } from '@angular/core'
import { TanStackField, injectForm } from '@tanstack/angular-form'
import { z } from 'zod'

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <ng-container
      [tanstackField]="form"
      name="age"
      [validators]="{
        onChange: z.number().gte(13, 'You must be 13 to make an account'),
      }"
      #age="field"
    >
      <!-- ... -->
    </ng-container>
  `,
})
export class AppComponent {
  form = injectForm({
    defaultValues: {
      age: 0,
    },
    onSubmit({ value }) {
      console.log(value)
    },
  })

  z = z
}

​
Async Schema Validation

import { Component } from '@angular/core'
import { TanStackField, injectForm } from '@tanstack/angular-form'
import { z } from 'zod'

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <ng-container
      [tanstackField]="form"
      name="age"
      [validators]="{
        onChange: z.number().gte(13, 'You must be 13 to make an account'),
        onChangeAsyncDebounceMs: 500,
        onChangeAsync: increaseAge
      }"
      #age="field"
    >
      <!-- ... -->
    </ng-container>
  `,
})
export class AppComponent {
  increaseAge = z.number().refine(
    async (value) => {
      const currentAge = await fetchCurrentAgeOnProfile()
      return value >= currentAge
    },
    {
      message: 'You can only increase the age',
    },
  )

  form = injectForm({
    defaultValues: {
      age: 0,
    },
    onSubmit({ value }) {
      console.log(value)
    },
  })

  z = z
}

​
Combining Schemas with Callbacks

For more control, combine schemas with callback functions: 
import { Component } from '@angular/core'
import { TanStackField, injectForm } from '@tanstack/angular-form'
import type { FieldValidateAsyncFn } from '@tanstack/angular-form'
import { z } from 'zod'

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <ng-container
      [tanstackField]="form"
      name="age"
      [validators]="{ onChangeAsync: ageValidator }"
      #age="field"
    >
      <!-- ... -->
    </ng-container>
  `,
})
export class AppComponent {
  ageValidator: FieldValidateAsyncFn<any, string, number> = async ({
    value,
    fieldApi,
  }) => {
    const errors = fieldApi.parseValueWithSchema(
      z.number().gte(13, 'You must be 13 to make an account'),
    )
    if (errors) return errors

    // Continue with your validation
  }

  // ...
}

​
Preventing Invalid Submissions

The form’s canSubmit flag indicates whether the form is valid and can be submitted: 
import { Component } from '@angular/core'
import { TanStackField, injectForm, injectStore } from '@tanstack/angular-form'

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <button type="submit" [disabled]="!canSubmit()">
      {{ isSubmitting() ? '...' : 'Submit' }}
    </button>
  `,
})
export class AppComponent {
  form = injectForm({
    defaultValues: {
      firstName: '',
    },
    onSubmit({ value }) {
      console.log(value)
    },
  })

  canSubmit = injectStore(this.form, (state) => state.canSubmit)
  isSubmitting = injectStore(this.form, (state) => state.isSubmitting)
}
The canSubmit flag is true until the form is touched, even if fields are technically invalid. Combine it with isPristine to prevent submission before any interaction: !canSubmit || isPristine.

​
Complete Example

Here’s a full validation example with sync and async validators: 
import { Component } from '@angular/core'
import { TanStackField, injectForm, injectStore } from '@tanstack/angular-form'
import type {
  FieldValidateAsyncFn,
  FieldValidateFn,
} from '@tanstack/angular-form'

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [TanStackField],
  template: `
    <form (submit)="handleSubmit($event)">
      <div>
        <ng-container
          [tanstackField]="form"
          name="firstName"
          [validators]="{
            onChange: firstNameValidator,
            onChangeAsyncDebounceMs: 500,
            onChangeAsync: firstNameAsyncValidator,
          }"
          #firstName="field"
        >
          <label [for]="firstName.api.name">First Name:</label>
          <input
            [id]="firstName.api.name"
            [name]="firstName.api.name"
            [value]="firstName.api.state.value"
            (blur)="firstName.api.handleBlur()"
            (input)="firstName.api.handleChange($any($event).target.value)"
          />
          @if (firstName.api.state.meta.isTouched) {
            @for (error of firstName.api.state.meta.errors; track $index) {
              <div style="color: red">
                {{ error }}
              </div>
            }
          }
          @if (firstName.api.state.meta.isValidating) {
            <p>Validating...</p>
          }
        </ng-container>
      </div>
      <div>
        <ng-container [tanstackField]="form" name="lastName" #lastName="field">
          <label [for]="lastName.api.name">Last Name:</label>
          <input
            [id]="lastName.api.name"
            [name]="lastName.api.name"
            [value]="lastName.api.state.value"
            (blur)="lastName.api.handleBlur()"
            (input)="lastName.api.handleChange($any($event).target.value)"
          />
        </ng-container>
      </div>
      <button type="submit" [disabled]="!canSubmit()">
        {{ isSubmitting() ? '...' : 'Submit' }}
      </button>
      <button type="reset" (click)="form.reset()">Reset</button>
    </form>
  `,
})
export class AppComponent {
  firstNameValidator: FieldValidateFn<any, string, any> = ({ value }) =>
    !value
      ? 'A first name is required'
      : value.length < 3
        ? 'First name must be at least 3 characters'
        : undefined

  firstNameAsyncValidator: FieldValidateAsyncFn<any, string, any> = async ({
    value,
  }) => {
    await new Promise((resolve) => setTimeout(resolve, 1000))
    return value.includes('error') && 'No "error" allowed in first name'
  }

  form = injectForm({
    defaultValues: {
      firstName: '',
      lastName: '',
    },
    onSubmit({ value }) {
      console.log(value)
    },
  })

  canSubmit = injectStore(this.form, (state) => state.canSubmit)
  isSubmitting = injectStore(this.form, (state) => state.isSubmitting)

  handleSubmit(event: SubmitEvent) {
    event.preventDefault()
    event.stopPropagation()
    this.form.handleSubmit()
  }
}

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