To implement authentication in Laravel 12 and later versions using Sanctum, follow these steps:

🔐 For web.php Routes:

Laravel Sanctum uses session-based authentication for routes defined in web.php. This works out of the box if you're already using the default Laravel authentication system (e.g., login via form, CSRF protection, etc.).

🔐 For api.php Routes:

For API routes, Sanctum expects token-based authentication. To access these routes:

First, generate a token for the user:

$token = $user->createToken('api-token')->plainTextToken;

Then, in your API requests, include the token in the Authorization header like this:

Authorization: Bearer <your-token-here>

This token is stored in the personal_access_tokens table and is used to authenticate API requests.

Read Official Doc

Laravel < 12

you can follow this Stackoverflow thread.