How to prevent MongoDB from returning the object ID while finding a document?

To prevent MongoDB from returning the Object ID while finding a document, you need to set _id to 0 in the projection parameter of the find() method. This excludes the _id field from the query results.

Syntax

db.collection.find(
    { query },
    { "_id": 0, "field1": 1, "field2": 1 }
);

Sample Data

Let us first create a collection with a sample document ?

db.preventObjectIdDemo.insertOne({
    "StudentName": "Chris",
    "StudentDetails": [
        {
            "StudentTotalScore": 540,
            "StudentCountryName": "US"
        },
        {
            "StudentTotalScore": 489,
            "StudentCountryName": "UK"
        }
    ]
});

{
    "acknowledged": true,
    "insertedId": ObjectId("5ca20a9c66324ffac2a7dc63")
}

Example 1: Default Query (With _id)

First, let's see the default behavior where _id is included ?

db.preventObjectIdDemo.find().pretty();

{
    "_id": ObjectId("5ca20a9c66324ffac2a7dc63"),
    "StudentName": "Chris",
    "StudentDetails": [
        {
            "StudentTotalScore": 540,
            "StudentCountryName": "US"
        },
        {
            "StudentTotalScore": 489,
            "StudentCountryName": "UK"
        }
    ]
}

Example 2: Exclude _id Field

Now, let's exclude the _id field by setting it to 0 in the projection ?

db.preventObjectIdDemo.find(
    {},
    { "_id": 0 }
).pretty();

{
    "StudentName": "Chris",
    "StudentDetails": [
        {
            "StudentTotalScore": 540,
            "StudentCountryName": "US"
        },
        {
            "StudentTotalScore": 489,
            "StudentCountryName": "UK"
        }
    ]
}

Example 3: Exclude _id with Specific Field Selection

You can also combine _id exclusion with specific field selection ?

db.preventObjectIdDemo.find(
    {},
    { "StudentName": 1, "_id": 0 }
).pretty();

{
    "StudentName": "Chris"
}

Key Points

• Set "_id": 0 in the projection parameter to exclude the Object ID.
• The _id field is included by default in all MongoDB queries.
• You can combine _id exclusion with other field projections.

Conclusion

Use {"_id": 0} in the projection parameter of find() to prevent MongoDB from returning the Object ID. This provides cleaner output when the _id field is not needed in your results.