In waterbath canning sterilizing jars is not needed as long as processing time is more than 10 minutes. Most recipes call for at least 10 minutes processing time or more.
Processing for more than 10 minutes sterilizes both the food and the jars.
You also do not need to sterilize for pressure canning. Everything will be well sterilized by the high heat involved in pressure processing.
Before every use, wash empty jars in hot water with detergent and rinse well by hand, or wash in a dishwasher. Unrinsed detergents may cause unnatural flavors and colors. These washing methods do not sterilize jars. Scale or hard-water films on jars are easily removed by soaking jars several hours in a solution containing 1 cup of vinegar (5 percent acidity) per gallon of water.
Sterilization of Empty Jars
All jams, jellies, and pickled products processed less than 10 minutes should be filled into sterile empty jars. To sterilize empty jars, put them right side up on the rack in a boiling-water canner. Fill the canner and jars with hot (not boiling) water to 1 inch above the tops of the jars. Boil 10 minutes at altitudes of less than 1,000 ft. At higher elevations, boil 1 additional minute for each additional 1,000 ft elevation. Remove and drain hot sterilized jars one at a time. Save the hot water for processing filled jars. Fill jars with food, add lids, and tighten screw bands.
Empty jars used for vegetables, meats, and fruits to be processed in a pressure canner need not be presterilized. It is also unnecessary to presterilize jars for fruits, tomatoes, and pickled or fermented foods that will be processed 10 minutes or longer in a boiling-water canner.
You must however always start with clean jars. Always wash your jars before you do any type of canning. I am assuming you would know that all equipment needs to be clean before any canning.
I don't personally use any recipes that call for less than 10 minutes, I am at high altitude and everything has time added. So I always simply start with clean jars.
If you do have a recipe that calls for less than 10 minutes you might consider adding time to your processing. This way you can simply skip this step. It is up to you.
Go ahead and check your recipe, does it call for less than 10 minutes processing time? Don't forget to figure you altitude. If so you should be sterilizing first.
Or if you've been sterilizing your jars and you are just more comfortable doing so, don't stop. It certainly won't hurt anything. Go ahead and sterilize the jars and have peace of mind.
Continue with your canning recipe.
Here are some ideas for keeping those jars warm before you fill them. Keeping Canning Jars Hot