I just saw a YouTube short that reminded me that sometimes common knowledge isn't common for everyone, SO here's the reason WHY you should not have a traditional mattress rawdogging the floor without a bedframe:
Hint β it's NOT because it makes your bedroom look like a frat boy's first apartment who spent all his money on a giant TV (also on the floor) and a ps5 and one sad mattress on the floor. (Although this is also a good reason, to avoid being that guy, it is not the actually important reason.)
You will get mold or mildew under your mattress if the mattress doesn't have air circulation happening underneath it. Air circulation is possible when the mattress is lifted up off of the floor with a bed frame, or if you have a floor mattress, when you regularly roll the mattress back up off the floor.
Do not just dump a mattress on the floor and leave it there.
You are a warm sweaty body lying on a mattress at night and all the sweat, moisture, and oils will get trapped between the mattress and your floor if there's no circulation. If you have a floor/tatami style mattress, you actually have to be frequently rolling that back up and moving it for the same reason.
Traditional floor mattresses get put away (taken off the floor) after sleeping, which brings in the necessary air circulation!
don't give yourself a moldy or mildewy mattress β those things are expensive.
The cheapest options are:
buy the cheapest frame you can find when you buy a mattress
or buy the super basic frame that comes with the mattress as a bundle offer
find a used mattress frame somewhere for free or cheap. Facebook marketplace, buy nothing, used furniture stores, estate sales, moving giveaways, whatever.
DIY a mattress frame if you have the time, energy, knowledge, and can find supplie
Buy a floor mattress you are committed to regularly rolling or folding up to provide air circulation
There is no "just put the mattress on the floor" option unless you want your bed to also function as a petri dish.