Is it safe charge my phone via usb in my macbook pro sleeping

I use my MacBook Pro in clamshell mode, plugged in 24 hours a day. During the day, I use a USB cable to charge my peripherals (mouse, keyboard, and headset). At night, I leave the Mac in sleep mode. I would like to know if it’s safe to leave my cellphone charging on the same cable overnight, every night. I tested it, and it works—even in sleep mode, I can charge the cellphone. I just wonder if it’s safe to do this in the long term. Thank you in advance.