How do I make case-insensitive queries on MongoDB?

To make case-insensitive queries in MongoDB, use regular expressions with the i flag or the $regex operator. This allows you to match documents regardless of letter case variations.

Syntax

// Method 1: Regular Expression with i flag
db.collection.find({ "field": /pattern/i });

// Method 2: $regex operator
db.collection.find({ "field": { $regex: "pattern", $options: "i" } });

Sample Data

db.caseInsensitiveDemo.insertMany([
    {"UserName": "David"},
    {"UserName": "DAVID"},
    {"UserName": "david"},
    {"UserName": "Carol"},
    {"UserName": "Mike"},
    {"UserName": "Sam"},
    {"UserName": "daVID"}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c7f6fec8d10a061296a3c45"),
        ObjectId("5c7f6ff28d10a061296a3c46"),
        ObjectId("5c7f6ffa8d10a061296a3c47"),
        ObjectId("5c7f70008d10a061296a3c48"),
        ObjectId("5c7f70058d10a061296a3c49"),
        ObjectId("5c7f70098d10a061296a3c4a"),
        ObjectId("5c7f70138d10a061296a3c4b")
    ]
}

Method 1: Using Regular Expression

Find all variations of "david" regardless of case ?

db.caseInsensitiveDemo.find({UserName: /^david$/i });

{ "_id": ObjectId("5c7f6fec8d10a061296a3c45"), "UserName": "David" }
{ "_id": ObjectId("5c7f6ff28d10a061296a3c46"), "UserName": "DAVID" }
{ "_id": ObjectId("5c7f6ffa8d10a061296a3c47"), "UserName": "david" }
{ "_id": ObjectId("5c7f70138d10a061296a3c4b"), "UserName": "daVID" }

Method 2: Using $regex Operator

Alternative syntax using the $regex operator ?

db.caseInsensitiveDemo.find({
    "UserName": { $regex: "^david$", $options: "i" }
});

{ "_id": ObjectId("5c7f6fec8d10a061296a3c45"), "UserName": "David" }
{ "_id": ObjectId("5c7f6ff28d10a061296a3c46"), "UserName": "DAVID" }
{ "_id": ObjectId("5c7f6ffa8d10a061296a3c47"), "UserName": "david" }
{ "_id": ObjectId("5c7f70138d10a061296a3c4b"), "UserName": "daVID" }

Key Points

• The i flag makes the regex case-insensitive
• ^ and $ ensure exact match (start and end of string)
• Both methods produce identical results
• Regular expressions are slower than exact matches, so use indexes when possible

Conclusion

MongoDB supports case-insensitive queries through regular expressions with the i flag or the $regex operator. Use ^pattern$ for exact matches and just pattern for partial matches.