jacaranda generates helper methods based on your model validations.

Json Schema Client is a Ruby client for JsonSchema with validation and hypermedia.

Validation of popular Polish codes, such as PESEL, NIP, REGON, post codes, car registration numbers, credit card numbers and anything really that can be helpful in advanced commercial application for Polish customers.

Plinko helps you create validators that collect all validation errors instead of breaking on the first failure.

Create K-fold splits from data files and assist in training and testing (useful for cross-validation in supervised machine learning)

If you want to decouple validations from model it would be probably the easiest solution

Logstash filter plugin for Auth0 JWT validation.

Mail validation for ActiveModel

µValidator is a zero dependency validation library, which mimics ActiveModel::Error behaviour

Adds parameter validation and error control to interactor

A method construction and validation toolkit.

Methodic : provide Hash table options arguments manager (specifications and validations

MinHTTP allows one to send and receive raw HTTP requests. It's a very thin wrapper around EventMachine's connect method with some SSL validation added.

Provides data class validation for active-model objects

Wrap validation conditions with a single command

Handle validation, coercion, and attributes.

Tiny plugin for MongoMapper to strip whitespace from strings before validation.

Adds the association and validation macros for Rspec in the same way Shoulda does for ActiveRecord.

An ActiveModel extension that strips tags from attributes before validation using the strip-tags helper.

JSON Data Definition Format validation for Ruby