A lot of people have used ESP8266 to add inexpensive WiFi connectivity to their projects, but [Oscar] decided to take it one step further and program an Arduino over WiFi with the ESP8266. [Oscar] … ...

Im not sure if the esp8266 chip its self is 5v tolerant, but I did at one time try to use 5v with the esp8266 esp-01 and it was fine for about 3 minutes and then it wasnt the esp that failed, but ...