If you didn’t specify a Seccomp profile, then Docker uses built-in Seccomp configuration.
For some reason, if you wish to run a container without any Seccomp profile, then you can override this by using --security-opt flag with unconfined flag:
docker run -d --security-opt seccomp=unconfined --name nginx-no-seccomp nginx
To see if your container runs without Seccomp profile, exec into it and check the status of Seccomp:
$ docker exec -it nginx-no-seccomp bash
root@ff4af1e85453:/# grep Seccomp /proc/$$/status
Seccomp: 0
Seccomp_filters: 0
You will see Seccomp: 0, which means the container is running without the default Seccomp profile.