How can I rename a field for all documents in MongoDB?

To rename a field for all documents in MongoDB, use the $rename operator with an empty query filter to match all documents. This operation updates the field name across the entire collection.

Syntax

db.collectionName.updateMany(
    {},
    { $rename: { "oldFieldName": "newFieldName" } }
);

Sample Data

Let's create a collection with student documents ?

db.renameFieldDemo.insertMany([
    { "StudentName": "John" },
    { "StudentName": "Carol" },
    { "StudentName": "Bob" },
    { "StudentName": "David" },
    { "StudentName": "Maxwell" }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c7ee6c7559dd2396bcfbfbb"),
        ObjectId("5c7ee6cb559dd2396bcfbfbc"),
        ObjectId("5c7ee6cf559dd2396bcfbfbd"),
        ObjectId("5c7ee6d3559dd2396bcfbfbe"),
        ObjectId("5c7ee6d8559dd2396bcfbfbf")
    ]
}

Display all documents to verify the current structure ?

db.renameFieldDemo.find();

{ "_id": ObjectId("5c7ee6c7559dd2396bcfbfbb"), "StudentName": "John" }
{ "_id": ObjectId("5c7ee6cb559dd2396bcfbfbc"), "StudentName": "Carol" }
{ "_id": ObjectId("5c7ee6cf559dd2396bcfbfbd"), "StudentName": "Bob" }
{ "_id": ObjectId("5c7ee6d3559dd2396bcfbfbe"), "StudentName": "David" }
{ "_id": ObjectId("5c7ee6d8559dd2396bcfbfbf"), "StudentName": "Maxwell" }

Example: Rename Field for All Documents

Rename the field "StudentName" to "StudentFirstName" for all documents ?

db.renameFieldDemo.updateMany(
    {},
    { $rename: { "StudentName": "StudentFirstName" } }
);

{
    "acknowledged": true,
    "matchedCount": 5,
    "modifiedCount": 5
}

Verify Result

Check the documents to confirm the field has been renamed ?

db.renameFieldDemo.find();

{ "_id": ObjectId("5c7ee6c7559dd2396bcfbfbb"), "StudentFirstName": "John" }
{ "_id": ObjectId("5c7ee6cb559dd2396bcfbfbc"), "StudentFirstName": "Carol" }
{ "_id": ObjectId("5c7ee6cf559dd2396bcfbfbd"), "StudentFirstName": "Bob" }
{ "_id": ObjectId("5c7ee6d3559dd2396bcfbfbe"), "StudentFirstName": "David" }
{ "_id": ObjectId("5c7ee6d8559dd2396bcfbfbf"), "StudentFirstName": "Maxwell" }

Key Points

• Use updateMany() for modern MongoDB versions instead of the legacy update() method.
• An empty filter {} matches all documents in the collection.
• The operation only affects documents that contain the specified field.

Conclusion

The $rename operator with updateMany() efficiently renames fields across all documents in a collection. Use an empty query filter to target all documents and ensure the operation completes successfully.