multiple 110v to arduino input pin

My project is to build a plug tester with an arduino. if anyone is unfamiliar with that, electricians use them to see if the plug has power to it and to see if it is wired correctly. I want to build one that displays a virtual plug tester via a webpage. I am using sparkfun ESP32 Thing as the brains and to host the webpage (unless someone can suggest a better route to go). to power it i plan on using a cell phone charger since it is 5v output. I know there are a few ways to take the 110v plug power and input it to one of the pins on the ESP32 but none of the ways i know seem to be the best. I can use 3 relays, one for each of the plugs wires. using 3 relays is going to make the unit too large, unless someone knows of a very small one. I am not sure if using a DPDT relay would allow me the control i need, basically just be able to know if there is power on the line or not. i could step down the volts for each of the plugs wires. i think this would make it even larger than using relays.
If anyone could provide a little guidance for me id thank you.

What if you used Neon indicators that are in black tubes with an LDR. Everything will be isolated from the mains AC.

The H11AA1 optocouplers are designed for safe interfacing of microprocessor inputs to AC lines, and are very easy to use.

I have never been exposed to an optocoupler. how would i interface with it? is it simply a dumb item that needs no code to control? i see everything but the pin diagram on it. what are the 6 feet for? can it control all three lines or would i need 3 optocouplers for the 3 ac lines?

Consult the data sheet for connections. You will need two resistors and one optocoupler for each AC line to be monitored.

For 110 VAC on input, use a 33K resistor (about 5 mA current, maximum) in the hot lead. 10K should be fine on the output.

If there is any chance (i.e. you live in north America) that the hot/neutral input polarity could be reversed, put resistors on both input lines as shown below.