Is Crucial Ram scanner safe to use, if not is there an alternative one?

I use Crucial all the time.  Most of the RAM they sell on the site is the same RAM you would get if you were buying it directly from the manufacturer.  Their free tool for determining which memory you have and what you need is one of the best around.  Use it all the time to determine what is in PCs and what will be compatible if I need to increase the amount of memory.

But I will often take the information from the tool and then search around for the same memory from other sites.  Crucial does not always have the best prices for the memory.

(25+ years in IT support.  Do this for a living.)

i've used it several times and it seemed safe to me

It's fine, it doesn't access your personal files nor install anything surreptitiously.