Whether you are making jam, tomato sauce, or pickles, if they are processed less than 10 minutes, you will need to prepare the jars you plan on using ahead of time. Some canning recipes specify that you need to use sterilized jars, but they don't always tell you how to actually sterilize them. Here are some simple instructions for safely sterilizing jars.
Keep in mind—this is the only method you should use to sterilize jars.
You may come across misinformation that says you can sterilize jars in a dishwasher or oven, but neither of these methods is considered safe by the USDA.
What You Need
If you don't have a home canning kit, you will need a few items to complete the sterilization process, including canning jars, a boiling water canner or large pot with a rack, and a jar lifter. The canning jars should be made of tempered glass with a two-piece vacuum cap (the metal screw band and flat, rubber-lined metal lid). If you are using a large pot, it needs to be at least two inches taller than the jars and be fitted with a rack and a lid. And if you don't have jar lifters you can use tongs.
What to Do
Once you have all of your equipment in place, the actually sterilizing should take about 25 minutes or so.
Place the empty jars right-side-up in the boiling water canner or large pot. You may use the same pot you will be using as a boiling water bath to can the jars once they are filled with food.
Completely cover the jars with hot (but not boiling) water—the water should be one inch above the top of the jars. Bring the water to a boil over high heat.
Once the water reaches a full rolling boil, begin timing. Boil the jars for 15 minutes.
Turn off the heat. If you are not quite ready to fill the sterilized jars and proceed with canning your recipe, you can leave them in the hot water for up to one hour. If you wait longer than an hour, you'll need to sterilize them again.
Remove the jars using jar lifters or tongs and drain well.
Note: Do not boil the canning lids as this can harm their adhesive rings. Instead, add the canning lids to the hot water after you turn off the heat when the jars have finished boiling.