In programming, a guard is a common pattern of controlling program flow. It involves performing a conditional check to determine whether the code execution should continue or exit. The use of guards can improve the readability and maintainability of your code.

Guards in NestJS work in a similar way as in general programming, but its implementation is tightly integrated with the NestJS framework. The responsibility of Guards is to allow or deny access to the NestJS endpoints. For instance, we can create a guard to protect a route that updates a user’s profile, to only be accessible by an administrator.