Subvalid allows you to use a familiar syntax to define validator classes to validate plain objects. Rather than hard coding single validation logic into the objects themselves, different validation logic can be used depending on the context.

Email address validation using RFC 822 pattern matching regular expressions

To comply with simple email validation to RFC5322.

gem for email validation

ActiveRecord uniqueness validations without raceconditions

Provides really basic postcode validation (intended for eCommerce platforms).

named_validations names to arguments of active_model's validates method.

Extension for default Rails validations. Adds some useful methods.

The validation is to compare values between web page values and mobile api responses

Client Side Validations for Rails 4

phone_validator makes phone validation natural for ActiveModel 3+ objects. Validation using global_phone.

Validate graphql-ruby arguments easily with dry-validation

Simple client validation messages

DataMapper plugin for performing validations on data models

Performs k-fold cross-validation on machine learning classifiers.

Ardm fork of dm-validations

Generates: controller file with actions specified in arguments, schema file for param validation written using dry-validation gem, use case class for handling logic of the request, presenter class for serialization of objects, request rspec specs for proper testing

Use Validation for Email in ruby

Find and report ActiveRecord validation errors.

A notifier for form validation errors.