Built-in Validators

Formify ships 35+ validators. Each has a dedicated page below covering every supported way to use it.

Two ways to use a validator

Every validator can be used in two interchangeable styles:

1. Config flag in a validationSchema

validationSchema: {
  email: { required: true, email: true },
}

A true value enables the rule. Passing a string overrides its message:

email: { email: "Enter a valid email" }

Parameterized rules use a value instead of true — minLength: 8, or a tuple to override the message: minLength: [8, "Too short"].

2. Composable rule from the V builder

V produces reusable Rule objects for the v1-style validators array and advanced composition:

import { V } from "formify-js";

const schema = {
  email: {
    required: true,
    validators: [
      { validator: V.email(), message: "Enter a valid email" },
    ],
  },
};

Empty-value semantics

Only required fails on empty input. Every other rule validates the value when present, so optional fields work without extra ceremony — combine a rule with required: true when the field must be filled.

What counts as empty: "", null, undefined, and empty arrays.

Validator pages

Presence & format

• required — value must not be empty
• email — email address
• url — http/https/ftp URL
• phone — international phone number
• uuid — UUID v1–v5
• ip — IPv4 or IPv6 (ip, ipv4, ipv6)

Character classes

• alpha — letters only
• alphanumeric — letters + digits
• numeric — number or numeric string
• integer — integer
• decimal — decimal number
• strong-password — strong password policy
• uppercase / lowercase — case-only strings
• no-whitespace — no whitespace
• special-characters — at least one special character
• trimmed — no leading/trailing spaces
• contains-uppercase, contains-lowercase, contains-number, contains-special — granular character checks

Dates, times & identifiers

• date — valid date
• time — HH:mm(:ss)
• zip — US ZIP code
• ssn — Social Security Number
• ein — Employer ID
• hex-color — #fff / #ffffff
• mac-address — MAC address
• isbn — ISBN-10 / ISBN-13
• domain — domain name
• username — 3–20 chars: letters, digits, _ .
• slug — lowercase letters, digits, hyphens
• base64 — base64 string
• hex — hexadecimal string
• latitude / longitude — geographic coordinates

Length & ranges

• min-length / max-length — string length
• min / max — numeric bounds
• between — numeric range
• pattern — custom regex
• array-length — array length range
• file-extension — allowed file extensions

Choice & relations

• one-of / not-one-of — membership
• confirm — match another field
• starts-with / ends-with / includes — string relations

Beyond individual rules

• composition — V.all, V.any, V.not, V.optional
• messages — how error messages are resolved (i18n)
• regexval — v1 compatibility helpers