Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Mongoose supports Node.js and Deno (alpha).
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.
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First install Node.js and MongoDB, then install the mongoose package using your preferred package manager:
npm install mongoosepnpm add mongooseyarn add mongoosebun add mongooseMongoose 6.8.0 also includes alpha support for Deno.
// Using Node.js `require()`constmongoose=require('mongoose');// Using ES6 importsimportmongoosefrom'mongoose';Or, using Deno's createRequire() for CommonJS support as follows.
import{createRequire}from'https://deno.land/std@0.177.0/node/module.ts';constrequire=createRequire(import.meta.url);constmongoose=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.jsMongoose Studio is a free, fully open-source, browser-based MongoDB GUI built by the Mongoose team for apps that already use Mongoose. Install @mongoosejs/studio from npm and run it alongside your app as Express middleware, or deploy it on Vercel or Netlify, to browse and edit documents, query with your existing models and schemas with autocomplete, build dashboards, visualize and edit GeoJSON, and use AI-assisted MongoDB workflows without moving data into a hosted third-party workspace or sharing raw MongoDB connection strings.
Available as part of the Tidelift Subscription
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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.
awaitmongoose.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.
Models are defined through the Schema interface.
constSchema=mongoose.Schema;constObjectId=Schema.ObjectId;constBlogPost=newSchema({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:
constComment=newSchema({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 setterComment.path('name').set(function(v){returncapitalize(v);});// middlewareComment.pre('save',function(next){notify(this.get('email'));next();});Once we define a model through mongoose.model('ModelName', mySchema), we can access it through the same function
constMyModel=mongoose.model('ModelName');Or just do it all at once
constMyModel=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
constMyModel=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:
constinstance=newMyModel();instance.my.key='hello';awaitinstance.save();Or we can find documents from the same collection
awaitMyModel.find({});You can also findOne, findById, update, etc.
constinstance=awaitMyModel.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:
constconn=mongoose.createConnection('your connection string');constMyModel=conn.model('ModelName',schema);constm=newMyModel();awaitm.save();// worksvs
constconn=mongoose.createConnection('your connection string');constMyModel=mongoose.model('ModelName',schema);constm=newMyModel();awaitm.save();// does not work b/c the default connection object was never connectedIn 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 modelconstBlogPost=mongoose.model('BlogPost');// create a blog postconstpost=newBlogPost();// create a commentpost.comments.push({title: 'My comment'});awaitpost.save();The same goes for removing them:
constpost=awaitBlogPost.findById(myId);post.comments[0].deleteOne();awaitpost.save();Embedded documents enjoy all the same features as your models. Defaults, validators, middleware.
See the docs page.
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 Documentthis.emit('set',path,val);// Pass control to the next prenext();});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,functionfirstPre(next,methodArg1,methodArg2){// Mutate methodArg1next('altered-'+methodArg1.toString(),methodArg2);});// pre declaration is chainableschema.pre(method,functionsecondPre(next,methodArg1,methodArg2){console.log(methodArg1);// => 'altered-originalValOfMethodArg1'console.log(methodArg2);// => 'originalValOfMethodArg2'// Passing no arguments to `next` automatically passes along the current argument values// i.e., the following `next()` is equivalent to `next(methodArg1, methodArg2)`// and also equivalent to, with the example method arg// values, `next('altered-originalValOfMethodArg1', 'originalValOfMethodArg2')`next();});type, when used in a schema has special meaning within Mongoose. If your schema requires using type as a nested property you must use object notation:
newSchema({broken: {type: Boolean},asset: {name: String,type: String// uh oh, it broke. asset will be interpreted as String}});newSchema({works: {type: Boolean},asset: {name: String,type: {type: String}// works. asset is an object with a type property}});Mongoose is built on top of the official MongoDB Node.js driver. Each mongoose model keeps a reference to a native MongoDB driver collection. The collection object can be accessed using YourModel.collection. However, using the collection object directly bypasses all mongoose features, including hooks, validation, etc. The one
notable exception is that YourModel.collection still buffers
commands. As such, YourModel.collection.find() will not
return a cursor.
Mongoose API documentation, generated using dox and acquit.
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