Band Aid

Ok, so here we have a CANTRIP that can: 

1. Just pick up everyone who falls in Battle and isnt outright killed, making Spare the dying absolutely pointless, since its just better in every aspect. 

2. Can be picked by EVERY Caster Class, with a power level that gives no excuse to not pick it

3. Will just heal the whole party to full after every encounter, eliminating the need for short rests unless its to refresh Cooldowns. 

Yeah, sry, this spell is broken beyond belive. 

If you want this spell a bit less broken: Change it to "gives temp HP" instead of outright healing.

Will that make it balanced? No, because its still literally False life as a Cantrip. But at least its not just an infinite source of instant healing… 

A cantrip for healing, without limits?  How about using the healer's own hit die to heal up the player in a fight. There's a limit to lay on hands for the sake of not breaking the hell out of the game, this should probably be revised to reflect some sort of limitation.  Maybe even sacrificing the healer's own constitution to help a conscious creature?

But written as is, wow this is super broken.

Healing Word already deals 1d4 + spell cast mod of healing.

This is why before one makes a homebrew to check through the book and see if it's already been done and like you said this negates any reason to take spare the dying.

Probably would change it to say the player adds 1d4 healing to short rest recovery, like a "hey you still need to tend to your wounds in battle but here's a little boost for you in case you get some bad rolls, at least it'll do you till a long rest"

Even then I could see a player saying that since it's a cantrip they can stack as many d4s as they want and effectively get full health on short rests no matter what.

I mean I guess that could be fixed by making it have concentration

Guys my homebrew spell is a cantrip that forces the enemy to make a DC 35 Con save or take 1000 damage it's super balanced can I use it in the campaign