Interface MongoOptions

Parsed Mongo Client Options.

User supplied options are documented by MongoClientOptions.

NOTE: The client's options parsing is subject to change to support new features. This type is provided to aid with inspection of options after parsing, it should not be relied upon programmatically.

Options are sourced from:

  • connection string
  • options object passed to the MongoClient constructor
  • file system (ex. tls settings)
  • environment variables
  • DNS SRV records and TXT records

Not all options may be present after client construction as some are obtained from asynchronous operations.


  • Required<Pick<MongoClientOptions, "autoEncryption" | "connectTimeoutMS" | "directConnection" | "driverInfo" | "forceServerObjectId" | "minHeartbeatFrequencyMS" | "heartbeatFrequencyMS" | "localThresholdMS" | "maxConnecting" | "maxIdleTimeMS" | "maxPoolSize" | "minPoolSize" | "monitorCommands" | "noDelay" | "pkFactory" | "raw" | "replicaSet" | "retryReads" | "retryWrites" | "serverSelectionTimeoutMS" | "socketTimeoutMS" | "srvMaxHosts" | "srvServiceName" | "tlsAllowInvalidCertificates" | "tlsAllowInvalidHostnames" | "tlsInsecure" | "waitQueueTimeoutMS" | "zlibCompressionLevel">>
  • SupportedNodeConnectionOptions
    • MongoOptions


[featureFlag: symbol]: any


ALPNProtocols?: string[] | Uint8Array | Uint8Array[]

An array of strings or a Buffer naming possible ALPN protocols. (Protocols should be ordered by their priority.)

appName?: string
autoEncryption: AutoEncryptionOptions

Optionally enable in-use auto encryption


Automatic encryption is an enterprise only feature that only applies to operations on a collection. Automatic encryption is not supported for operations on a database or view, and operations that are not bypassed will result in error (see libmongocrypt: Auto Encryption Allow-List). To bypass automatic encryption for all operations, set bypassAutoEncryption=true in AutoEncryptionOpts.

Automatic encryption requires the authenticated user to have the listCollections privilege action.

If a MongoClient with a limited connection pool size (i.e a non-zero maxPoolSize) is configured with AutoEncryptionOptions, a separate internal MongoClient is created if any of the following are true:

  • AutoEncryptionOptions.keyVaultClient is not passed.
  • AutoEncryptionOptions.bypassAutomaticEncryption is false.

If an internal MongoClient is created, it is configured with the same options as the parent MongoClient except minPoolSize is set to 0 and AutoEncryptionOptions is omitted.

ca?: string | Buffer | (string | Buffer)[]

Optionally override the trusted CA certificates. Default is to trust the well-known CAs curated by Mozilla. Mozilla's CAs are completely replaced when CAs are explicitly specified using this option.

cert?: string | Buffer | (string | Buffer)[]

Cert chains in PEM format. One cert chain should be provided per private key. Each cert chain should consist of the PEM formatted certificate for a provided private key, followed by the PEM formatted intermediate certificates (if any), in order, and not including the root CA (the root CA must be pre-known to the peer, see ca). When providing multiple cert chains, they do not have to be in the same order as their private keys in key. If the intermediate certificates are not provided, the peer will not be able to validate the certificate, and the handshake will fail.

checkServerIdentity?: ((hostname, cert) => Error | undefined)

Type declaration

    • (hostname, cert): Error | undefined
    • Verifies the certificate cert is issued to hostname.

      Returns Error object, populating it with reason, host, and cert on failure. On success, returns undefined.

      This function is intended to be used in combination with thecheckServerIdentity option that can be passed to connect and as such operates on a certificate object. For other purposes, consider using x509.checkHost() instead.

      This function can be overwritten by providing an alternative function as theoptions.checkServerIdentity option that is passed to tls.connect(). The overwriting function can call tls.checkServerIdentity() of course, to augment the checks done with additional verification.

      This function is only called if the certificate passed all other checks, such as being issued by trusted CA (

      Earlier versions of Node.js incorrectly accepted certificates for a givenhostname if a matching uniformResourceIdentifier subject alternative name was present (see CVE-2021-44531). Applications that wish to acceptuniformResourceIdentifier subject alternative names can use a customoptions.checkServerIdentity function that implements the desired behavior.


      • hostname: string

        The host name or IP address to verify the certificate against.

      • cert: PeerCertificate

        A certificate object representing the peer's certificate.

      Returns Error | undefined



ciphers?: string

Cipher suite specification, replacing the default. For more information, see modifying the default cipher suite. Permitted ciphers can be obtained via tls.getCiphers(). Cipher names must be uppercased in order for OpenSSL to accept them.

compressors: ("none" | "snappy" | "zlib" | "zstd")[]
connectTimeoutMS: number

The time in milliseconds to attempt a connection before timing out.

credentials?: MongoCredentials
crl?: string | Buffer | (string | Buffer)[]

PEM formatted CRLs (Certificate Revocation Lists).

dbName: string
directConnection: boolean

Allow a driver to force a Single topology type with a connection string containing one host

driverInfo: DriverInfo

Allows a wrapping driver to amend the client metadata generated by the driver to include information about the wrapping driver

ecdhCurve?: string

A string describing a named curve or a colon separated list of curve NIDs or names, for example P-521:P-384:P-256, to use for ECDH key agreement. Set to auto to select the curve automatically. Use crypto.getCurves() to obtain a list of available curve names. On recent releases, openssl ecparam -list_curves will also display the name and description of each available elliptic curve. Default: tls.DEFAULT_ECDH_CURVE.

family?: number
forceServerObjectId: boolean

Force server to assign _id values instead of driver

heartbeatFrequencyMS: number

heartbeatFrequencyMS controls when the driver checks the state of the MongoDB deployment. Specify the interval (in milliseconds) between checks, counted from the end of the previous check until the beginning of the next one.

hints?: number
hosts: HostAddress[]
key?: string | Buffer | (string | Buffer | KeyObject)[]

Private keys in PEM format. PEM allows the option of private keys being encrypted. Encrypted keys will be decrypted with options.passphrase. Multiple keys using different algorithms can be provided either as an array of unencrypted key strings or buffers, or an array of objects in the form {pem: <string|buffer>[, passphrase: ]}. The object form can only occur in an array. object.passphrase is optional. Encrypted keys will be decrypted with object.passphrase if provided, or options.passphrase if it is not.

loadBalanced: boolean
localAddress?: string
localPort?: number
localThresholdMS: number

The size (in milliseconds) of the latency window for selecting among multiple suitable MongoDB instances.

lookup?: LookupFunction
maxConnecting: number

The maximum number of connections that may be in the process of being established concurrently by the connection pool.

maxIdleTimeMS: number

The maximum number of milliseconds that a connection can remain idle in the pool before being removed and closed.

maxPoolSize: number

The maximum number of connections in the connection pool.

metadata: ClientMetadata
minDHSize?: number
minHeartbeatFrequencyMS: number

Sets the minimum heartbeat frequency. In the event that the driver has to frequently re-check a server's availability, it will wait at least this long since the previous check to avoid wasted effort.

minPoolSize: number

The minimum number of connections in the connection pool.

monitorCommands: boolean

Enable command monitoring for this client

noDelay: boolean

TCP Connection no delay

passphrase?: string

Shared passphrase used for a single private key and/or a PFX.

pfx?: string | Buffer | (string | Buffer | PxfObject)[]

PFX or PKCS12 encoded private key and certificate chain. pfx is an alternative to providing key and cert individually. PFX is usually encrypted, if it is, passphrase will be used to decrypt it. Multiple PFX can be provided either as an array of unencrypted PFX buffers, or an array of objects in the form {buf: <string|buffer>[, passphrase: ]}. The object form can only occur in an array. object.passphrase is optional. Encrypted PFX will be decrypted with object.passphrase if provided, or options.passphrase if it is not.

pkFactory: PkFactory

A primary key factory function for generation of custom _id keys

proxyHost?: string
proxyPassword?: string
proxyPort?: number
proxyUsername?: string
raw: boolean

Enabling the raw option will return a Node.js Buffer which is allocated using allocUnsafe API. See this section from the Node.js Docs here for more detail about what "unsafe" refers to in this context. If you need to maintain your own editable clone of the bytes returned for an extended life time of the process, it is recommended you allocate your own buffer and clone the contents:


const raw = await collection.findOne({}, { raw: true });
const myBuffer = Buffer.alloc(raw.byteLength);
myBuffer.set(raw, 0);
// Only save and use `myBuffer` beyond this point


Please note there is a known limitation where this option cannot be used at the MongoClient level (see NODE-3946). It does correctly work at Db, Collection, and per operation the same as other BSON options work.

readConcern: ReadConcern
readPreference: ReadPreference
rejectUnauthorized?: boolean

If true the server will reject any connection which is not authorized with the list of supplied CAs. This option only has an effect if requestCert is true.


replicaSet: string

Specifies the name of the replica set, if the mongod is a member of a replica set.

retryReads: boolean

Enables retryable reads.

retryWrites: boolean

Enable retryable writes.

secureContext?: SecureContext

An optional TLS context object from tls.createSecureContext()

secureProtocol?: string

Legacy mechanism to select the TLS protocol version to use, it does not support independent control of the minimum and maximum version, and does not support limiting the protocol to TLSv1.3. Use minVersion and maxVersion instead. The possible values are listed as SSL_METHODS, use the function names as strings. For example, use 'TLSv1_1_method' to force TLS version 1.1, or 'TLS_method' to allow any TLS protocol version up to TLSv1.3. It is not recommended to use TLS versions less than 1.2, but it may be required for interoperability. Default: none, see minVersion.

serverApi: ServerApi
serverSelectionTimeoutMS: number

Specifies how long (in milliseconds) to block for server selection before throwing an exception.

servername?: string
session?: Buffer

An optional Buffer instance containing a TLS session.

socketTimeoutMS: number

The time in milliseconds to attempt a send or receive on a socket before the attempt times out.

srvHost?: string
srvMaxHosts: number

The maximum number of hosts to connect to when using an srv connection string, a setting of 0 means unlimited hosts

srvServiceName: string

Modifies the srv URI to look like:


Querying this DNS URI is expected to respond with SRV records

tls: boolean


If tls is provided as an option, it is equivalent to setting the ssl option.

NodeJS native TLS options are passed through to the socket and retain their original types.

Additional options:

nodejs native option driver spec equivalent option name driver option type
ca tlsCAFile string
crl tlsCRLFile string
cert tlsCertificateKeyFile string
key tlsCertificateKeyFile string
passphrase tlsCertificateKeyFilePassword string
rejectUnauthorized tlsAllowInvalidCertificates boolean
checkServerIdentity tlsAllowInvalidHostnames boolean
see note below tlsInsecure boolean

If tlsInsecure is set to true, then it will set the node native options checkServerIdentity to a no-op and rejectUnauthorized to false.

If tlsInsecure is set to false, then it will set the node native options checkServerIdentity to a no-op and rejectUnauthorized to the inverse value of tlsAllowInvalidCertificates. If tlsAllowInvalidCertificates is not set, then rejectUnauthorized will be set to true.

Note on tlsCAFile, tlsCertificateKeyFile and tlsCRLFile

The files specified by the paths passed in to the tlsCAFile, tlsCertificateKeyFile and tlsCRLFile fields are read lazily on the first call to MongoClient.connect. Once these files have been read and the ca, cert, crl and key fields are populated, they will not be read again on subsequent calls to MongoClient.connect. As a result, until the first call to MongoClient.connect, the ca, cert, crl and key fields will be undefined.

tlsAllowInvalidCertificates: boolean

Bypasses validation of the certificates presented by the mongod/mongos instance

tlsAllowInvalidHostnames: boolean

Disables hostname validation of the certificate presented by the mongod/mongos instance.

tlsCAFile?: string
tlsCRLFile?: string
tlsCertificateKeyFile?: string
tlsInsecure: boolean

Disables various certificate validations.

waitQueueTimeoutMS: number

The maximum time in milliseconds that a thread can wait for a connection to become available.

writeConcern: WriteConcern
zlibCompressionLevel: 0 | 3 | 9 | 4 | 1 | 2 | 5 | 6 | 7 | 8

An integer that specifies the compression level if using zlib for network compression.

Generated using TypeDoc