Which input validation method is considered more secure than client-side validation?

Server-side input validation is considered more secure than client-side validation because it occurs on the server after data is submitted by the user, ensuring that any data being processed meets the necessary criteria regardless of what has occurred on the client's machine.

Client-side validation can enhance user experience by providing immediate feedback and reducing server load, but it can be easily bypassed by users who manipulate their client environment, disable JavaScript, or send direct requests to the server. Therefore, relying solely on client-side checks can leave systems vulnerable to attacks, as malicious users can submit data that has not undergone proper sanitization or validation.

In contrast, server-side validation is essential for maintaining the integrity and security of applications. It provides a second layer of defense, allowing the server to enforce proper data formats, constraints, and business rules before any processing takes place. This ensures that any potentially harmful or improperly formatted input is caught before it can lead to security threats such as SQL injection or cross-site scripting (XSS).