Delete a field and value in MongoDB?

To delete a field and its value from MongoDB documents, use the $unset operator. This operator removes the specified field from all matched documents in the collection.

Syntax

db.collection.update(
    { field: { $exists: true } },
    { $unset: { fieldName: 1 } },
    { multi: true }
)

Sample Data

Let us first create a collection with sample documents −

db.deleteFieldDemo.insertMany([
    { "FirstName": "John", "LastName": "Smith" },
    { "FirstName": "David", "LastName": "Miller" },
    { "FirstName": "Carol", "LastName": "Taylor" }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5cb9fb767219729fde21ddad"),
        ObjectId("5cb9fb837219729fde21ddae"),
        ObjectId("5cb9fb8d7219729fde21ddaf")
    ]
}

Display all documents from the collection −

db.deleteFieldDemo.find().pretty();

{
    "_id": ObjectId("5cb9fb767219729fde21ddad"),
    "FirstName": "John",
    "LastName": "Smith"
}
{
    "_id": ObjectId("5cb9fb837219729fde21ddae"),
    "FirstName": "David",
    "LastName": "Miller"
}
{
    "_id": ObjectId("5cb9fb8d7219729fde21ddaf"),
    "FirstName": "Carol",
    "LastName": "Taylor"
}

Example: Delete FirstName Field

Remove the "FirstName" field from all documents −

db.deleteFieldDemo.updateMany(
    { FirstName: { $exists: true } },
    { $unset: { FirstName: 1 } }
);

{
    "acknowledged": true,
    "matchedCount": 3,
    "modifiedCount": 3
}

Verify Result

Check if the FirstName field has been deleted −

db.deleteFieldDemo.find().pretty();

{ "_id": ObjectId("5cb9fb767219729fde21ddad"), "LastName": "Smith" }
{ "_id": ObjectId("5cb9fb837219729fde21ddae"), "LastName": "Miller" }
{ "_id": ObjectId("5cb9fb8d7219729fde21ddaf"), "LastName": "Taylor" }

Conclusion

The $unset operator effectively removes fields from MongoDB documents. Use updateMany() with $exists: true to delete a field from all documents that contain it.