# Introduction to the Principle

There are two types of CRDTs: Op-based CRDTs and State-based CRDTs. This article
focuses on the concept of Op-based CRDTs.

Op-based CRDTs operate on the principle that if two users perform identical
sequences of operations, the final state of the document should also be
identical. To achieve this, each user saves all the operations performed on the
data (Operations) and synchronizes these Operations with other users to ensure a
consistent final state. A critical challenge in this approach is ensuring the
order of Operations remains consistent, especially when parallel modification
operations occur. To address this, Op-based CRDTs require that all possible
parallel Operations be commutative, satisfying the final consistency
requirement.