What is the default value of the _id field in MongoDB projections?

In MongoDB, when projecting documents, the default value of the _id field is 1. This means that when you retrieve documents from a collection, the _id field will be included in the result set by default unless explicitly excluded.

The _id field is a special field that acts as a unique identifier for each document within a collection. By default, MongoDB automatically generates a unique ObjectId for the _id field if it is not provided when documents are created. Therefore, it is included in query results to ensure that each document can be uniquely identified.

It's important to note that if you specify a projection that explicitly sets the _id field to 0, you are opting to exclude it from your results. However, if you do not explicitly include or exclude the _id field in your query projections, it will be included by default due to its importance in document identification in MongoDB collections.