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UTF-8 Validation

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  • Overview
  • Specify the UTF-8 Validation Setting
  • Set the Validation Scope

In this guide, you can learn how to enable or disable the Node.js driver's UTF-8 validation feature. UTF-8 is a character encoding specification that ensures compatibility and consistent presentation across most operating systems, applications, and language character sets.

If you enable validation, the driver throws an error when it attempts to convert data that contains invalid UTF-8 characters. The validation adds processing overhead since it needs to check the data.

If you disable validation, your application avoids the validation processing overhead, but cannot guarantee consistent presentation of invalid UTF-8 data.

The driver enables UTF-8 validation by default. It checks documents for any characters that are not encoded in a valid UTF-8 format when it transfers data between your application and MongoDB.


The current version of the Node.js driver automatically substitutes invalid UTF-8 characters with alternate valid UTF-8 ones before validation when you send data to MongoDB. Therefore, the validation only throws an error when the setting is enabled and the driver receives invalid UTF-8 document data from MongoDB.

Read the sections below to learn how to set UTF-8 validation using the Node.js driver.

You can specify whether the driver performs UTF-8 validation by defining the enableUtf8Validation setting in the options parameter when you create a client, reference a database or collection, or call a CRUD operation. If you omit the setting, the driver enables UTF-8 validation.

See the following for code examples that demonstrate how to disable UTF-8 validation on the client, database, collection, or CRUD operation:

// disable UTF-8 validation on the client
new MongoClient('<connection uri>', { enableUtf8Validation: false });
// disable UTF-8 validation on the database
client.db('<database name>', { enableUtf8Validation: false });
// disable UTF-8 validation on the collection
db.collection('<collection name>', { enableUtf8Validation: false });
// disable UTF-8 validation on a specific operation call
await myColl.findOne({ title: 'Cam Jansen'}, { enableUtf8Validation: false });

If your application reads invalid UTF-8 from MongoDB while the enableUtf8Validation option is enabled, it throws a BSONError that contains the following message:

Invalid UTF-8 string in BSON document

The enableUtf8Validation setting automatically applies to the scope of the object instance on which you included it, and any other objects created by calls on that instance.

For example, if you include the option on the call to instantiate a database object, any collection instance you construct from that object inherits the setting. Any operations you call on that collection instance also inherit the setting.

const database = client.db('books', { enableUtf8Validation: false });
// The collection inherits the UTF-8 validation disabled setting from the database
const myColl = database.collection('mystery');
// CRUD operation runs with UTF-8 validation disabled
await myColl.findOne({ title: 'Encyclopedia Brown' });

You can override the setting at any level of scope by including it when constructing the object instance or when calling an operation.

For example, if you disable validation on the collection object, you can override the setting in individual CRUD operation calls on that collection.

const collection = database.collection('mystery', { enableUtf8Validation: false });
// CRUD operation runs with UTF-8 validation enabled
await myColl.findOne({ title: 'Trixie Belden' }, { enableUtf8Validation: true });
// CRUD operation runs with UTF-8 validation disabled
await myColl.findOne({ title: 'Enola Holmes' });


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