Simple clean validation errors that can be used independently

Ernr builds on the power of Rails 3 validations. It lets you use validations to identify situations which are warnings rather than errors. It also lets you define a callback on the model which is executed after save if there are any warnings.

emailvalidation.io provides an email validation & verification API. Automate email validation & verification without any user interaction.

Common usage for Taiwan validation

Validate graphql-ruby arguments easily with dry-validation

Simple client side validation that keeps validation in the models

Sequel plugin which provides sexy validations for model.

A Ruby implementation of the General Gameplay Notation (GGN) specification. GGN is a rule-agnostic, JSON-based format for describing pseudo-legal board-to-board transformations in abstract strategy board games. This library provides parsing, validation, and evaluation capabilities for GGN documen...

Simple model and validation mixins for RubyMotion

A gem/plugin for Rails 3+ that enables client-side validation using ActiveModel + HTML5

Robust options validation for methods.

A Ruby wrapper for the World Wide Web Consortium’s online validation services.

Phone number parsing, validation and formatting

Includes a couple of core functions such as callbacks, timestamping, typecasting and lots of generic validation routines.

Rails plugin that maps model validations to class names on form elements to integrate with Validatious.

ActiveRecord Tableless Models provides a simple mixin for creating models that are not bound to the database. This approach is useful for taking advantage of the features of ActiveRecord such as validation, relationships, etc.

Regressor generates regression specs based on ActiveRecord models. Currently relations, validations, attributes, and database indexes are supported.

Add a validation filter to your controller.

Minimalist validation matcher

Introspects your database string field maximum lengths and automatically defines length validations.