This Is Why Your Brake Pedal Vibrate/pulsate When You Match Your Brake

There are some things which can cause the brake pedal vibrate or pulsate when you apply the brake of your car. The vibration and the pulsation is that machine-gun effect you feel on your leg when you apply the brake, especially a hard stop.
If you notice this effect each time you hard-brake, it can be traced to be your ABS.

Before we proceed, let’s get something about the brakes. The new style disc brakes offer wonderful stopping power and performance more than the old style drum brakes. This new disc brakes can be equipped with an Anti-lock Braking System (ABS) to help prevent your wheels from locking on braking hard, or braking in wet conditions.

ABS will give you this vibrating/pulsating feeling when you’re braking hard.
During normal braking other than hard braking, everything should be normal whether you have ABS fitted in the car or not.
In a nutshell, when you initiate hard braking, the anti-lock braking system may be activated, and hence, the vibrating/pulsating sensation.

High spots on rotors, warped rotors and thinning brake fluid can also cause the brake pedal to pulsate when there is no hard braking.