Find a document with ObjectID in MongoDB?

To find a document with ObjectId in MongoDB, use the ObjectId() constructor in your query to match the specific _id field value.

Syntax

db.collectionName.find({"_id": ObjectId("yourObjectIdValue")}).pretty();

Sample Data

Let us create a collection with sample documents to demonstrate finding by ObjectId ?

db.findDocumentWithObjectIdDemo.insertMany([
    {"UserName": "Larry"},
    {"UserName": "Mike", "UserAge": 23},
    {"UserName": "Carol", "UserAge": 26, "UserHobby": ["Learning", "Photography"]}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c90e4384afe5c1d2279d69b"),
        ObjectId("5c90e4444afe5c1d2279d69c"),
        ObjectId("5c90e4704afe5c1d2279d69d")
    ]
}

Display all documents to see the generated ObjectIds ?

db.findDocumentWithObjectIdDemo.find().pretty();

{ "_id": ObjectId("5c90e4384afe5c1d2279d69b"), "UserName": "Larry" }
{
    "_id": ObjectId("5c90e4444afe5c1d2279d69c"),
    "UserName": "Mike",
    "UserAge": 23
}
{
    "_id": ObjectId("5c90e4704afe5c1d2279d69d"),
    "UserName": "Carol",
    "UserAge": 26,
    "UserHobby": [
        "Learning",
        "Photography"
    ]
}

Example 1: Find Carol's Document

db.findDocumentWithObjectIdDemo.find({"_id": ObjectId("5c90e4704afe5c1d2279d69d")}).pretty();

{
    "_id": ObjectId("5c90e4704afe5c1d2279d69d"),
    "UserName": "Carol",
    "UserAge": 26,
    "UserHobby": [
        "Learning",
        "Photography"
    ]
}

Example 2: Find Mike's Document

db.findDocumentWithObjectIdDemo.find({"_id": ObjectId("5c90e4444afe5c1d2279d69c")}).pretty();

{
    "_id": ObjectId("5c90e4444afe5c1d2279d69c"),
    "UserName": "Mike",
    "UserAge": 23
}

Key Points

• Always wrap the ObjectId string with ObjectId() constructor in queries
• ObjectId queries return at most one document since _id is unique
• Use .pretty() for formatted output display

Conclusion

Finding documents by ObjectId requires using the ObjectId() constructor with the string value. This is the most efficient way to retrieve a specific document since _id is automatically indexed.