Use a dedicated microphone: Built-in laptop or phone mics often struggle with the heavy low-end of a beatbox kick or the sharp transients of a snare.
Loopy Pro (iOS): Widely considered the king of mobile looping. It is highly modular, meaning you can design your own interface. Its "one-tap" recording makes it perfect for fast-paced beatbox routines. download loopstation beatbox
Get an Audio Interface: If using a computer, an interface like a Focusrite Scarlett will significantly reduce "latency"—the tiny delay between when you make a sound and when the software records it. Use a dedicated microphone: Built-in laptop or phone