What is the difference between applying a pipe at the param level vs handler level vs globally in NestJS?
Param-level applies the pipe to a single argument only. Handler-level (@UsePipes on the method) runs the pipe for all arguments of that handler. Controller-level applies to all handlers in the controller. Global applies to every request across the entire app. The global ValidationPipe is the standard for most apps.
Pipe binding at all four levels
Choosing the right binding level:
Param-level — for transformation pipes like ParseIntPipe, ParseUUIDPipe on specific params.
Handler-level — when only some routes need validation with specific options.
Controller-level — when all routes in the controller share the same validation rules.
Global — for ValidationPipe in most apps; register via APP_PIPE for DI support.