Coding⏱️ 2 min read📅 2026-05-31

How to Fix: What's Mongoose error Cast to ObjectId failed for value XXX at path "_id"?

Mongoose error Cast to ObjectId failed for value XXX at path “_id”. The problem is that the _id field in your MongoDB document does not match the format expected by Mongoose.

Quick Answer: Use the correct format for the _id field, which should be a string of 12 hexadecimal digits separated by underscores (e.g., 41224d776a326fb40f000001). You can use the toObjectId function in Mongoose to convert the value to an ObjectId.

📋 Table of Contents

  1. 🚀 How to Resolve This Issue
  2. 💡 Conclusion

The error 'Cast to ObjectId failed for value XXX at path "_id"' occurs when Mongoose is unable to parse the provided _id value into an ObjectId. This can happen if the _id value is not in the correct format, which is usually a 12-character hexadecimal string.

🚀 How to Resolve This Issue

Method 1: Use the toString() Method

  1. Step 1: In your find() method, use the toString() method to convert the _id value into a string.

Method 2: Use the id() Method

  1. Step 1: In your find() method, use the id() method to get the _id value as a string.

💡 Conclusion

By applying one of these methods, you should be able to resolve the 'Cast to ObjectId failed for value XXX at path "_id"' error and successfully retrieve your data.

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