Mongoose

Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Mongoose supports Node.js and Deno (alpha).

Documentation

The official documentation website is mongoosejs.com.

Mongoose 9.0.0 was released on November 21, 2025. You can find more details on backwards breaking changes in 9.0.0 on our docs site.

Support

• Stack Overflow
• Bug Reports
• Mongoose Slack Channel
• Help Forum
• MongoDB Support

Plugins

Check out the plugins search site to see hundreds of related modules from the community. Next, learn how to write your own plugin from the docs or this blog post.

Contributors

Pull requests are always welcome! Please base pull requests against the master branch and follow the contributing guide.

If your pull requests makes documentation changes, please do not modify any .html files. The .html files are compiled code, so please make your changes in docs/*.pug, lib/*.js, or test/docs/*.js.

View all 400+ contributors.

Installation

First install Node.js and MongoDB, then install the mongoose package using your preferred package manager:

Using npm

npm install mongoose

Using pnpm

pnpm add mongoose

Using Yarn

yarn add mongoose

Using Bun

bun add mongoose

Mongoose 6.8.0 also includes alpha support for Deno.

Importing

// Using Node.js `require()`
const mongoose = require('mongoose');

// Using ES6 imports
import mongoose from 'mongoose';

Or, using Deno's createRequire() for CommonJS support as follows.

import { createRequire } from 'https://deno.land/std@0.177.0/node/module.ts';
const require = createRequire(import.meta.url);

const mongoose = require('mongoose');

mongoose.connect('mongodb://127.0.0.1:27017/test')
  .then(() => console.log('Connected!'));

You can then run the above script using the following.

deno run --allow-net --allow-read --allow-sys --allow-env mongoose-test.js

Mongoose for Enterprise

Available as part of the Tidelift Subscription

The maintainers of mongoose and thousands of other packages are working with Tidelift to deliver commercial support and maintenance for the open source dependencies you use to build your applications. Save time, reduce risk, and improve code health, while paying the maintainers of the exact dependencies you use. Learn more.

Overview

Connecting to MongoDB

First, we need to define a connection. If your app uses only one database, you should use mongoose.connect. If you need to create additional connections, use mongoose.createConnection.

Both connect and createConnection take a mongodb:// URI, or the parameters host, database, port, options.

await mongoose.connect('mongodb://127.0.0.1/my_database');

Once connected, the open event is fired on the Connection instance. If you're using mongoose.connect, the Connection is mongoose.connection. Otherwise, mongoose.createConnection return value is a Connection.

Note: If the local connection fails then try using 127.0.0.1 instead of localhost. Sometimes issues may arise when the local hostname has been changed.

Important! Mongoose buffers all the commands until it's connected to the database. This means that you don't have to wait until it connects to MongoDB in order to define models, run queries, etc.

Defining a Model

Models are defined through the Schema interface.

const Schema = mongoose.Schema;
const ObjectId = Schema.ObjectId;

const BlogPost = new Schema({
  author: ObjectId,
  title: String,
  body: String,
  date: Date
});

Aside from defining the structure of your documents and the types of data you're storing, a Schema handles the definition of:

• Validators (async and sync)
• Defaults
• Getters
• Setters
• Indexes
• Middleware
• Methods definition
• Statics definition
• Plugins
• pseudo-JOINs

The following example shows some of these features:

const Comment = new Schema({
  name: { type: String, default: 'hahaha' },
  age: { type: Number, min: 18, index: true },
  bio: { type: String, match: /[a-z]/ },
  date: { type: Date, default: Date.now },
  buff: Buffer
});

// a setter
Comment.path('name').set(function(v) {
  return capitalize(v);
});

// middleware
Comment.pre('save', function(next) {
  notify(this.get('email'));
  next();
});

Take a look at the example in examples/schema/schema.js for an end-to-end example of a typical setup.

Accessing a Model

Once we define a model through mongoose.model('ModelName', mySchema), we can access it through the same function

const MyModel = mongoose.model('ModelName');

Or just do it all at once

const MyModel = mongoose.model('ModelName', mySchema);

The first argument is the singular name of the collection your model is for. Mongoose automatically looks for the plural version of your model name. For example, if you use

const MyModel = mongoose.model('Ticket', mySchema);

Then MyModel will use the tickets collection, not the ticket collection. For more details read the model docs.

Once we have our model, we can then instantiate it, and save it:

const instance = new MyModel();
instance.my.key = 'hello';
await instance.save();

Or we can find documents from the same collection

await MyModel.find({});

You can also findOne, findById, update, etc.

const instance = await MyModel.findOne({ /* ... */ });
console.log(instance.my.key); // 'hello'

For more details check out the docs.

Important! If you opened a separate connection using mongoose.createConnection() but attempt to access the model through mongoose.model('ModelName') it will not work as expected since it is not hooked up to an active db connection. In this case access your model through the connection you created:

const conn = mongoose.createConnection('your connection string');
const MyModel = conn.model('ModelName', schema);
const m = new MyModel();
await m.save(); // works

vs

const conn = mongoose.createConnection('your connection string');
const MyModel = mongoose.model('ModelName', schema);
const m = new MyModel();
await m.save(); // does not work b/c the default connection object was never connected

Embedded Documents

In the first example snippet, we defined a key in the Schema that looks like:

comments: [Comment]

Where Comment is a Schema we created. This means that creating embedded documents is as simple as:

// retrieve my model
const BlogPost = mongoose.model('BlogPost');

// create a blog post
const post = new BlogPost();

// create a comment
post.comments.push({ title: 'My comment' });

await post.save();

The same goes for removing them:

const post = await BlogPost.findById(myId);
post.comments[0].deleteOne();
await post.save();

Embedded documents enjoy all the same features as your models. Defaults, validators, middleware.

Middleware

See the docs page.

Intercepting and mutating method arguments

You can intercept method arguments via middleware.

For example, this would allow you to broadcast changes about your Documents every time someone sets a path in your Document to a new value:

schema.pre('set', function(next, path, val, typel) {
  // `this` is the current Document
  this.emit('set', path, val);

  // Pass control to the next pre
  next();
});

Moreover, you can mutate the incoming method arguments so that subsequent middleware see different values for those arguments. To do so, just pass the new values to next:

schema.pre(method, function firstPre(next, methodArg1, methodArg2