The general instructions for removing ketchup from fabrics, carpets and upholstry seems to be to scrape as much as you can off with a spoon or dull knife while trying to avoid working the stain further into the fabric. Then, pretreat with a detergent or with a homemade remedy of baking soda and hydrogen peroxide (testing first for colorfastness), then rinse with cold water and blot with a white cloth or sponge. Repeat as necessary. Some sites recommend using white vinegar after the rinse, but I think that’s mostly for clothing that can be fully laundered afterwards. On things that one can’t put in a washing machine, just keep rinsing and blotting thoroughly with a clean cloth.
But as always, I provide helpful links for you to explore the topic further, should you need to know this information, but why would you, you are probably not throwing ketchup around your house, unless you are:
"Queen of Clean: How to remove ketchup stains" on KY3
"How to Remove Ketchup Stains From Clothes, Carpet, and Upholstery" on The Spruce
"3 quick steps to get ketchup & tomato sauce stains out" on Grove Collaborative
Should we send this to PAB’s staff?
But...but what about the efficacy of treating the stain with club soda? That was always the route we took to remove stains from whatever. If you’re a debutante whose calfskin gloves are hopelessly stained with cucumber, reach for the club soda first.