Rails API parameter validation

RUT/RUN Chilean validator for Rails models

ISO Schematron Validation

Adds validation methods to ActiveModel for validating phone numbers.

Validation for serialized model objects

pure ruby PNG file manipulation & validation

MiniTest matchers for ActiveModel::Validations

JSON schema validation for Rails

Input Mask validation for ActiveModel

DB constraints in migrations similiar to ActiveRecord validations. Core classes

If you have a presence validation, you'll probably want a non-null constraint to go with it.

Validation and helper methods for string based enums in rails

Parameter whitelisting for Sinatra. Provides validation, defaults, and post-processing.

A simple, localizable EachValidator for URL fields in ActiveRecord 3.0.

ruby client library for the validator.nu HTML5 validation API

Used to validate ContentData objects.

ActiveModel validations for domains (including TLDs), ip addresses and email addresses with fully localization support.

Allows testing vor valid html (including html5) and css. In addition you can configure the gem to use a locally installed validation service instead of the online w3c servers

This gem allows you to conditionally validate your models, based on where in a multi-step process the user is.

An object that works with form_for that encapsulates validations and data management, leaving the business logic up to your testable old self.