If only it were that easy.  The filter on our 2009 KA fridge is the type mentioned above that twists out.  Since 2009, the available filters have changed from Whirlpool brand to another brand and yet another brand.  None have cross references.

If you want to be sure, remove the filter and bring it to the store with you to match it up.  No need to shut off the water supply.

I got into the habit of saving the information on the box from the new filter so I'd know the item/part number, but since the brands keep changing, that practice doesn't help anymore.

I don't change my filter every six months.  I reset the filter button for another six months.  I usually don't let it go for more than a year without changing it, but with just two of us we don't go through enough water to require replacement after only six months.

Some people even change them less frequently than that.

These filters are mainly charcoal, but since water in our area is predominantly groundwater and is treated with chlorine, there is a pronounced difference between a glass of tap water and filtered water when placed side by side.  The filter gets rid of the chlorine smell and overall improves the taste. 

I use the filtered stuff for drinking, making coffee, and making ice.  Other than that, I use water from the tap.

Also, on Whirlpool makes, you can remove the filter entirely and the ice maker and water dispenser will still work without the need for installing a bypass.

I think the flow rate slows down -- if it does -- so slowly that you don't notice it.  I don't know if I'm convincing myself that it has slowed down or not, as I only notice (or imagine it) when I'm filling the coffee carafe, but of course the replacement indicator light has suggestive powers that contribute to my speculation. 

I think the best way to test is to fill a glass halfway with tap water, and another halfway with dispenser water.  Get your nose in there and smell both.  Taste both too, if the smell test wasn't enough.  If there's little or no difference, it's time for a new filter.

https://www.ebay.com/itm/1PK-Refrigerato...

I change mine once a year...but...my water is already filtered when it gets to the fridge filter (it's tied into the under-sink filter line).

My fridge uses the filter that's down in the bottom grill under the freezer.  I get them on ebay too...genuine WP filters much cheaper than anywhere else.  My flow does not decrease either.

I should probably replace it water filter in my fridge because it's been more than 2 years since it's been changed.  The main reason being, it now only filters water for the ice maker, as water no longer flows through the door dispenser.  Over the period of a couple of years the flow slowly decrease until it got so slow, it would "time out" and stop before a glass was would fill half way (I gave up trying at that point), now the dispenser won't even drip.  I assume the supply line very slowly got so cold it froze, but who knows.

On my fridge (a Samsung french door) the "replace filter" light comes on every 6 months regardless of how much the water is being used.  I replaced it the first time at 6 months, then once a year after that because it was such a waste.   

I just looked up the filter for my fridge and they're $23 for 2 on Amazon.  Boy it's a good thing I don't have the newer version of this fridge as the filters are now $50 EACH!

That is a flimsy and ill-designed system.  Nothing like what's on my 2009 KA, which is solid, simple and nearly fool-proof.