---
title: Data Types
slug: v4-4/tAWkWoXz6TuRtoc-1VFVI
docTags:
createdAt: 2023-08-10T20:29:15.578Z
---
The conflict-free replicated data type (CRDT) data structure enables smooth peer‑to‑peer offline replication and online sync in distributed systems.
When multiple offline Ditto stores make concurrent updates to the same CRDT object, the CRDT merge mechanism remediates the data collision so that, when sync takes place, they converge to a consistent state. For more information, see the *Platform Manual *> [Sync and Replication Concepts](docId\:Vh2a6OTl4DLnEl0A-mIU8).
Following are the types of CRDTs you can use in Ditto:
:::hint{type="info"}
For an overview of documents, including fields and key-value pairs, see [Document Model](docId\:AmTy0OpHec33HDf-1IOhZ).
:::
- [Register](docId\:eeXDc_d-t6lR3VgGcO7Qy)
- [Map](docId\:ltCtHSbI4y0U7RnsWneJG)
- [Counter](docId\:Y7L-8jGjrdwl-3AePgpv2)
- [Attachment](docId\:slQOBcNXTyF-KeLi7l8F8)
# Supported Types Overview
The following table provides a quick overview of the advanced data types you can use in Ditto, along with their guiding principles for conflict resolution, or *merge semantics*, a brief description, and a common usage scenario:
| **Type** | **Merge Semantics** | **Description** | **Use Case** |
| ------------ | -------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------- |
| `register` | Last‑Write‑Wins Register,
Delta-state replication | Stores a single value and allows for concurrent updates. | Updates associated with later temporal timestamps *always* win. |
| `map` | Add-Wins Map,
Delta-state replication | Working in conjunction with the Register, stores the mapping of temporal timestamps to the values written in the Register to help resolve concurrency conflicts. | Make a list of items in a document and update those items over time. |
| `counter` | Positive or Negative Counter,
The sum of all `Site_ID` Counters,
Delta-state replication | Converts a number value for a given key into a Counter.
Unlike a primitive `number`, value increments and decrements merge without conflict. | Manage inventory and handle votes, such as stock details and survey results. |
| `attachment` | Last-Write‑Wins Register,
Merges only when explicitly fetched | Stores very large amounts of binary data, such as an image file, and allows for concurrent updates. | Reduce Small Peer resource usage by storing data outside of memory. |
| `array` | Last‑Write‑Wins Register,
Delta-state replication | An extension of the `register` type, | |
# Learning Resource: Interactive Tutorial
If you prefer learning by doing, see Jake Lazaroff's blog for a hands-on tutorial: "[An Interactive Intro to CRDTs](https://jakelazaroff.com/words/an-interactive-intro-to-crdts/)."
# Update Behavior by Type
The following table provides an overview of the CRDTs and associated behavior for a given operation:
:::hint{type="info"}
For more information, see [CRUD Operations](docId:1CEXFnSWhjeqa_R6yyL-8).
:::
| **Operation** | **Description** |
| ---------------------- | -------------------------------------------------------------------------------- |
| `set register` | Sets the value for a given field in the document. |
| `set map` | Sets value for a given field in the `map`. |
| `remove register` | Removes a value for a given field in the document. |
| `remove map` | Removes a value for a given key in the `map` structure. |
| `replace with counter` | Converts a `number` value for a given field into a `counter`. |
| `increment counter` | Unlike a `number`, increments the `counter` by the given positive integer value. |
| `decrement counter` | Unlike a `number`, decrements the `counter` by the given negative integer value. |