ChatGPT can significantly assist in writing authentication code by generating boilerplate for common flows like login, registration, and password reset. It can provide code snippets tailored to specific frameworks or libraries such as Node.js with Passport.js, Python with Django's built-in auth, or JWT implementation. Furthermore, ChatGPT offers valuable guidance on security best practices, including proper password hashing using bcrypt, secure token management, and protection against common vulnerabilities like SQL injection and XSS. It also helps with validation rules and error handling, making the authentication process more robust. Developers can leverage it to understand complex authentication concepts or even debug existing code efficiently, accelerating development and ensuring a secure implementation.