Fixing SyntaxError: Unexpected token < in JSON at position 0

Overview

The error message "SyntaxError: Unexpected token < in JSON at position 0" is commonly caused by trying to parse HTML as JSON. This can happen when an AJAX request is made to a server that returns HTML instead of JSON. In this article, we will discuss how to fix this error and avoid it in the future.

What is JSON?

JSON stands for JavaScript Object Notation and is a lightweight data interchange format. It is easy for humans to read and write, and easy for machines to parse and generate. JSON is a text format that is completely language independent but uses conventions that are familiar to programmers of the C family of languages.

Fixing the Error

To fix the "SyntaxError: Unexpected token < in JSON at position 0" error, you need to make sure that the server is returning valid JSON. Here are a few things you can try:

Check the server response

The first thing you should do is check the response from the server. Open your web browser's developer console and look at the network tab. Find the request that is causing the error and check the response. If it is HTML instead of JSON, then you have found the cause of the error.

Ensure the server is returning proper JSON

If the server is returning HTML instead of JSON, you need to modify the server to return the correct response. Make sure that the server is returning proper JSON with the correct MIME type, application/json.

Check the AJAX request

If the server is returning valid JSON, then the problem may be with the AJAX request. Check the AJAX request to make sure that the dataType is set to "json". If it is not set correctly, then the response may not be parsed as JSON.

Conclusion

The "SyntaxError: Unexpected token < in JSON at position 0" error can be frustrating, but it is easy to fix once you know the cause. By ensuring that the server is returning valid JSON and that the AJAX request is set up correctly, you can avoid this error in the future. Remember to always check the response from the server and make sure that it is what you are expecting.