this is a short review of Esp 8266 - 01 single channel wifi module.
here is a problem-solving solution if your Esp 01 relay module is not working.
I found a problem on this board when working with it. in this video, I clearly discuss how to solve the problem of this esp 01 single channel relay module.
this small board can be used for different IoT-based projects, for making Alarms & IoT-based security systems.