---
title: Introduction
nav_order: 1
layout: default
---

# Introduction

ShareDB is a full-stack library for realtime JSON document collaboration. It provides a Node.js server for coordinating and committing edits from multiple clients. It also provides a JavaScript client for manipulating documents, which can be run either in Node.js or in the browser.

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The underlying conflict management is handled through [Operational Transformation (OT)](https://en.wikipedia.org/wiki/Operational_transformation). The implementation of this strategy is delegated to ShareDB's type plugins.

## Features

 - Realtime synchronization of any JSON document
 - Concurrent multi-user collaboration
 - Synchronous editing API with asynchronous eventual consistency
 - Realtime query subscriptions
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 - Simple integration with any database
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 - Horizontally scalable with pub/sub integration
 - Projections to select desired fields from documents and operations
 - Middleware for implementing access control and custom extensions
 - Ideal for use in browsers or on the server
 - Offline change syncing upon reconnection
 - In-memory implementations of database and pub/sub for unit testing
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 - Access to historic document versions
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 - Realtime user presence syncing