connect-mongo

MongoDB session store for Connect and Express written in Typescript.

Breaking change in V4 and rewritten the whole project using Typescript. Please checkout the migration guide and changelog for details.

• Install
• Compatibility
• Usage
  • Express or Connect integration
  • Connection to MongoDB
• Known issues
  • Native autoRemove causing error on close
  • MongoError exports circular dependency
  • Existing encrypted v3.2.0 sessions are not decrypted correctly by v4
• Events
• Session expiration
• Remove expired sessions
  • Set MongoDB to clean expired sessions (default mode)
  • Set the compatibility mode
  • Disable expired sessions cleaning
• Lazy session update
• Transparent encryption/decryption of session data
• Options
  • Connection-related options (required)
  • More options
  • Crypto-related options
• Development
  • Example application
  • Release
• License

Install

npm install connect-mongo

• Install mongodb alongside connect-mongo; it is a required peer dependency so you pick the driver version that matches your cluster.
• If you are upgrading from v3.x to v4, please checkout the migration guide for details.
• If you are upgrading v4.x to latest version, you may check the example and options for details.

Compatibility

• Support Express up to 5.0
• Support native MongoDB driver >= 5.x (peer dependency range >=5.0.0, tested in CI with 5.x, 6.x, and 7.x)
• Support Node.js 20 LTS, 22 LTS and 24 (Current LTS)
• Support MongoDB server versions 4.4 - 8.0

We follow MongoDB's official Node.js driver compatibility tables and exercise every combination of the versions above (3 Node releases × 3 driver majors × 5 server tags) in CI so that mismatches surface quickly. Note that driver 5.x officially supports Node 20, while Node 22/24 coverage relies on driver 6.x/7.x, matching the upstream guidance.

For extended compatibility, see previous versions v3.x. But please note that we are not maintaining v3.x anymore.

Usage

Express or Connect integration

Express 4.x, 5.0 and Connect 3.x:

const session = require('express-session');
const MongoStore = require('connect-mongo');

app.use(session({
  secret: 'foo',
  store: MongoStore.create(options)
}));

import session from 'express-session'
import MongoStore from 'connect-mongo'

app.use(session({
  secret: 'foo',
  store: MongoStore.create(options)
}));

Connection to MongoDB

In many circumstances, connect-mongo will not be the only part of your application which need a connection to a MongoDB database. It could be interesting to re-use an existing connection.

Alternatively, you can configure connect-mongo to establish a new connection.

Create a new connection from a MongoDB connection string

MongoDB connection strings are the best way to configure a new connection. For advanced usage, more options can be configured with mongoOptions property.

// Basic usage
app.use(session({
  store: MongoStore.create({ mongoUrl: 'mongodb://localhost/test-app' })
}));

// Advanced usage
app.use(session({
  store: MongoStore.create({
    mongoUrl: 'mongodb://user12345:foobar@localhost/test-app?authSource=admin&w=1',
    mongoOptions: advancedOptions // See below for details
  })
}));

Re-use an existing native MongoDB driver client promise

In this case, you just have to give your MongoClient instance to connect-mongo.

/*
** There are many ways to create MongoClient.
** You should refer to the driver documentation.
*/

// Database name present in the connection string will be used
app.use(session({
  store: MongoStore.create({ clientPromise })
}));

// Explicitly specifying database name
app.use(session({
  store: MongoStore.create({
    clientPromise,
    dbName: 'test-app'
  })
}));

Known issues

Known issues in GitHub Issues page.

Native autoRemove causing error on close

• Calling close() immediately after creating the session store may cause error when the async index creation is in process when autoRemove: 'native'. You may want to manually manage the autoRemove index. #413

MongoError exports circular dependency

The following error can be safely ignored from official reply.

(node:16580) Warning: Accessing non-existent property 'MongoError' of module exports inside circular dependency
(Use `node --trace-warnings ...` to show where the warning was created)

Existing encrypted v3.2.0 sessions are not decrypted correctly by v4

v4 cannot decrypt the session encrypted from v3.2 due to a bug. Please take a look on this issue for possible workaround. #420

Events

A MongoStore instance will emit the following events:

| Event name | Description | Payload | ----- | ----- | ----- | | create | A session has been created | sessionId | | touch | A session has been touched (but not modified) | sessionId | | update | A session has been updated | sessionId | | set | A session has been created OR updated (for compatibility purpose) | sessionId | | destroy | A session has been destroyed manually | sessionId |

Session expiration

When the session cookie has an expiration date, connect-mongo will use it.

Otherwise, it will create a new one, using ttl option.

app.use(session({
  store: MongoStore.create({
    mongoUrl: 'mongodb://localhost/test-app',
    ttl: 14 * 24 * 60 * 60 // = 14 days. Default
  })
}));

Note: Each time a user interacts with the server, its session expiration date is refreshed.

Remove expired sessions

By default, connect-mongo uses MongoDB's TTL collection feature (2.2+) to have mongodb automatically remove expired sessions. But you can change this behavior.

Set MongoDB to clean expired sessions (default mode)

connect-mongo will create a TTL index for you at startup. You MUST have MongoDB 2.2+ and administration permissions.

app.use(session({
  store: MongoStore.create({
    mongoUrl: 'mongodb://localhost/test-app',
    autoRemove: 'native' // Default
  })
}));

Note: If you use connect-mongo in a very concurrent environment, you should avoid this mode and prefer setting the index yourself, once!

Set the compatibility mode

In some cases you can't or don't want to create a TTL index, e.g. Azure Cosmos DB.

connect-mongo will take care of removing expired sessions, using defined interval.

app.use(session({
  store: MongoStore.create({
    mongoUrl: 'mongodb://localhost/test-app',
    autoRemove: 'interval',
    autoRemoveInterval: 10 // In minutes. Default
  })
}));

Disable expired sessions cleaning

You are in production environnement and/or you manage the TTL index elsewhere.

app.use(session({
  store: MongoStore.create({
    mongoUrl: 'mongodb://localhost/test-app',
    autoRemove: 'disabled'
  })
}));

Lazy session update

If you are using express-session >= 1.10.0 and don't want to resave all the session on database every single time that the user refreshes the page, you can lazy update the session, by limiting a period of time.

app.use(express.session({
  secret: 'keyboard cat',
  saveUninitialized: false, // don't create session until something stored
  resave: false, //don't save session if unmodified
  store: MongoStore.create({
    mongoUrl: 'mongodb://localhost/test-app',
    touchAfter: 24 * 3600 // time period in seconds
  })
}));

by doing this, setting touchAfter: 24 * 3600 you are saying to the session be updated only one time in a period of 24 hours, does not matter how many request's are made (with the exception of those that change something on the session data)

Transparent encryption/decryption of session data

When working with sensitive session data it is recommended to use encryption.
Use the new cryptoAdapter option to plug in your encryption strategy. The preferred helper uses the Web Crypto API (AES-GCM):

import MongoStore, { createWebCryptoAdapter } from 'connect-mongo'

const store = MongoStore.create({
  mongoUrl: 'mongodb://localhost/test-app',
  cryptoAdapter: createWebCryptoAdapter({
    secret: process.env.SESSION_SECRET!,
  }),
})

If you need the legacy kruptein behavior, wrap it explicitly:

import { createKrupteinAdapter } from 'connect-mongo'

const store = MongoStore.create({
  mongoUrl: 'mongodb://localhost/test-app',
  cryptoAdapter: createKrupteinAdapter({ secret: 'squirrel' }),
})

The legacy crypto option still works for backwards compatibility; it is automatically wrapped into a kruptein-based adapter. Supplying both crypto and cryptoAdapter throws an error so it is clear which path is used.

Options

Connection-related options (required)

One of the following options should be provided. If more than one option are provided, each option will take precedence over others according to priority.

|Priority|Option|Description| |:------:|------|-----------| |1|mongoUrl|A connection string for creating a new MongoClient connection. If database name is not present in the connection string, database name should be provided using dbName option. | |2|clientPromise|A Promise that is resolved with MongoClient connection. If the connection was established without database name being present in the connection string, database name should be provided using dbName option.| |3|client|An existing MongoClient connection. If the connection was established without database name being present in the connection string, database name should be provided using dbName option.|

More options

|Option|Default|Description| |------|:-----:|-----------| |mongoOptions|{}|Options object forwarded to MongoClient.connect, e.g. TLS/SRV settings. Can be used with mongoUrl option.| |dbName||A name of database used for storing sessions. Can be used with mongoUrl, or clientPromise options. Takes precedence over database name present in the connection string.| |collectionName|'sessions'|A name of collection used for storing sessions.| |ttl|1209600|The maximum lifetime (in seconds) of the session which will be used to set session.cookie.expires if it is not yet set. Default is 14 days.| |autoRemove|'native'|Behavior for removing expired sessions. Possible values: 'native', 'interval' and 'disabled'.| |autoRemoveInterval|10|Interval (in minutes) used when autoRemove option is set to interval.| |touchAfter|0|Interval (in seconds) between session updates.| |timestamps|false|When true, stores createdAt (on insert) and updatedAt (on every write/touch) fields on each session document for auditing. Disabled by default to preserve existing schemas.| |stringify|true|If true, connect-mongo will serialize sessions using JSON.stringify before setting them, and deserialize them with JSON.parse when getting them. This is useful if you are using types that MongoDB doesn't support.| |serialize||Custom hook for serializing sessions to MongoDB. This is helpful if you need to modify the session before writing it out.| |unserialize||Custom hook for unserializing sessions from MongoDB. This can be used in scenarios where you need to support different types of serializations (e.g., objects and JSON strings) or need to modify the session before using it in your app.| |writeOperationOptions||Options object to pass to every MongoDB write operation call that supports it (e.g. update, remove). Useful for adjusting the write concern. Only exception: If autoRemove is set to 'interval', the write concern from the writeOperationOptions object will get overwritten.| |transformId||Transform original sessionId in whatever you want to use as storage key.| |cryptoAdapter||Preferred hook for encrypting/decrypting session payloads. Accepts any object with async encrypt/decrypt functions; helpers createWebCryptoAdapter (AES-GCM via Web Crypto API) and createKrupteinAdapter are provided.| |crypto||Crypto related options. See below.|

If you enable timestamps, each session document will include createdAt (first insert) and updatedAt (every subsequent set/touch) fields. These fields are informational only and do not change TTL behavior.

Crypto-related options (legacy)

Prefer cryptoAdapter for new integrations. The legacy crypto options are wrapped internally into a kruptein adapter to preserve backwards compatibility:

|Option|Default|Description| |------|:-----:|-----------| |secret|false|Enables transparent crypto in accordance with OWASP session management recommendations.| |algorithm|'aes-256-gcm'|Allows for changes to the default symmetric encryption cipher. See crypto.getCiphers() for supported algorithms.| |hashing|'sha512'|May be used to change the default hashing algorithm. See crypto.getHashes() for supported hashing algorithms.| |encodeas|'hex'|Specify to change the session data cipher text encoding.| |key_size|32|When using varying algorithms the key size may be used. Default value 32 is based on the AES blocksize.| |iv_size|16|This can be used to adjust the default IV size if a different algorithm requires a different size.| |at_size|16|When using newer AES modes such as the default GCM or CCM an authentication tag size can be defined.|

Development

npm install
docker compose up -d
npm run watch:test

TLS & SRV fixtures

• Generate local certificates once with npm run tls:setup (drops files in docker/tls).
• Launch the optional TLS container with docker compose -f docker-compose.yaml -f docker-compose.tls.yaml --profile tls up -d.
• Copy example/.env.example to example/.env and point MONGO_URL to the TLS port (mongodb://root:[email protected]:27443/example-db?authSource=admin). Add MONGO_TLS_CA_FILE=../docker/tls/ca.crt so the driver trusts the self-signed CA. Set MONGO_TLS_CERT_KEY_FILE=../docker/tls/client.pem if you need mutual TLS.
• To exercise SRV/TLS against a managed cluster (Atlas, DocumentDB, CosmosDB), set MONGO_URL to your mongodb+srv:// string and either MONGO_TLS_CA_FILE or NODE_EXTRA_CA_CERTS to the provider CA bundle. The example scripts automatically reuse those settings in every variant (plain JS, Mongoose, and TS).

Example application

# from the repo root
cp example/.env.example example/.env
npm link
cd example
npm link "connect-mongo"   # optional if you want live code from this checkout
npm install
npm run start:js
# or npm run start:mongoose / npm run start:ts

After the first run you can edit example/.env to swap between the local docker fixture, the TLS profile, or any mongodb+srv:// cluster without changing the code.

Release

Until the GitHub release workflow lands, do the manual flow:

1. Bump version, update CHANGELOG.md and README. Commit and push.
2. Run npm test && npm run build (build uses tsdown to emit dual ESM/CJS bundles to dist/).
3. Publish: npm publish
4. Tag: git tag vX.Y.Z && git push --tags

License

The MIT License