Validation

Overview

mobx-formkit ships with a pluggable validation system. You can choose one or more validation backends (called drivers) and attach them to the form at initialization. Each driver is responsible for validating each field and pushing error messages into the field's validationErrorStack.

Validation can be triggered:

• Automatically — on field blur, change, form init, submit, clear, reset (configurable via options)
• Manually — via form.validate(), field.validate(), or form.submit()

For a deeper dive into the validation lifecycle (what happens when, in what order), see the Validation Lifecycle page.

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Choosing a Validation Plugin

Style	Driver	Best For	Example
Custom functions	VJF	Full control, custom logic, server checks	({ field }) => [field.value.length > 3, 'Too short']
Declarative rules	DVR	Simple string-based rules (like Laravel)	'required or email or min:5'
JSON Schema	AJV	JSON-first projects, API compatibility	{ type: 'string', minLength: 3 }
Object schema	YUP	Modern JS/TS, chainable API	y.string().required().min(3)
Object schema	JOI	Enterprise-grade, rich error messages	j.string().min(3).required()
TypeScript schema	ZOD	TypeScript-first, type inference	z.string().min(3)
TypeScript schema	VALIBOT	Tiny TS-first schemas, sync only	v.pipe(v.string(), v.minLength(3))
TypeScript schema	VINEJS	Sync rules, async validation API	vine.string().minLength(3)

When to use what

Use Case	Recommended
Simple forms with basic rules	DVR — fastest to write
Full control over validation logic	VJF — write any function
JSON Schema compliance (API validation)	AJV — standards-based
Modern object-oriented validation	YUP — popular, good DX
Enterprise / complex schemas	JOI — battle-tested, rich errors
TypeScript-native with infer	ZOD — best TS integration
Tiny TypeScript-first schemas (sync)	VALIBOT — smallest bundle, sync pipes
Sync rules with async API	VINEJS — promise-based validation

Can I use multiple plugins?

Yes. You can enable multiple plugins simultaneously. Validation runs through all enabled drivers in sequence (configurable via validationPluginsOrder). If stopValidationOnError is true, subsequent drivers are skipped once a field has an error.

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Plugin Comparison

Feature	VJF	DVR	AJV	YUP	JOI	ZOD	VALIBOT	VINEJS
Custom validation functions	✅ Native	❌	❌	❌	❌	❌	❌	❌
String-based rules	❌	✅	❌	❌	❌	❌	❌	❌
JSON Schema	❌	❌	✅	❌	❌	❌	❌	❌
Chainable API	❌	❌	❌	✅	✅	✅	✅	✅
Async validation	✅	✅	✅	❌	❌	❌	❌	✅
Extend with custom rules	✅	✅	✅	❌	❌	❌	✅	✅
Automatic error messages	User-defined	✅	✅	✅	✅	✅	✅	✅
TypeScript inference	No	No	No	Partial	Partial	✅	✅	✅

VJF, DVR, AJV, VALIBOT and VINEJS support custom extension (via the extend callback). VJF, DVR, AJV and VINEJS support the async validation pipeline. YUP, JOI and ZOD do not support the extend callback — they rely on their own native APIs for those features. VALIBOT is sync-only (use native pipe/check/custom() for async-style logic).

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Setup Pages

Choose your plugin

• Setup VJF — Vanilla JavaScript Functions
• Setup DVR — Declarative Validation Rules
• Setup AJV — Schema Validation Keywords
• Setup YUP — Object Schema Validator
• Setup JOI — Object Schema Validator
• Setup ZOD — TypeScript-First Schema Validation
• Setup VALIBOT — Tiny TypeScript-First Schema Validation
• Setup VINEJS — Sync Rules, Async Validation API

Extend with custom rules

Available only for VJF, DVR, AJV, VALIBOT and VINEJS.

• Extend VJF — Custom Validation Functions
• Extend DVR — Custom Declarative Rules
• Extend AJV — Custom JSON Schema Keywords
• Extend VALIBOT — Custom Valibot Checks
• Extend VINEJS — Custom VineJS Rules

Async validation

Available only for VJF, DVR, AJV and VINEJS.

• Async VJF
• Async DVR
• Async AJV
• Async VINEJS

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Related Guides

• Validation Lifecycle — when validation fires, field filtering, plugin ordering
• Error Handling — submitThrowsError, defaultGenericError, server error mapping
• Performance & SSR — validationDebounceWait, stopValidationOnError, validation triggers
• Validation & Submit Actions — validate(), submit(), check(), invalidate()
• Validation Hooks — onSuccess, onError, extending hooks