Difference between find() and findOne() methods in MongoDB?

The findOne() method returns the first document if a query matches, otherwise returns null. The find() method never returns null ? it always returns a cursor object, even when no documents match.

Syntax

// findOne() - returns single document or null
db.collection.findOne(query, projection);

// find() - returns cursor object
db.collection.find(query, projection);

Sample Data

Let us create an empty collection to demonstrate the behavior ?

db.createCollection('emptyCollection');

{ "ok" : 1 }

Check the document count in the collection ?

db.emptyCollection.count();

0

Example 1: findOne() on Empty Collection

Test findOne() behavior when no documents exist ?

if(db.emptyCollection.findOne()){
    print("Returns Document");
} else {
    print("Returns null");
}

Returns null

Example 2: find() on Empty Collection

Test find() behavior when no documents exist ?

if(db.emptyCollection.find()){
    print("Returns Cursor");
} else {
    print("Returns null");
}

Returns Cursor

Key Differences

Conclusion

Use findOne() when you need a single document and want null-checking capability. Use find() when you need multiple documents or want consistent cursor-based processing regardless of result count.