Prepare your pressure canner according to the manufacturer's instructions.
Wash your canning jars and prepare your lids and rings.
Wash the carrots well. Peel them, then wash them again.
Slice or dice the carrots into your preferred size.
Bring a pot or kettle of fresh water to a boil.
Pack the raw carrots firmly into the jars, leaving 1 inch of headspace.
Add salt if desired. Use 1/2 teaspoon per pint or 1 teaspoon per quart.
Pour boiling water over the carrots, leaving 1 inch of headspace.
Remove air bubbles. Check the headspace again and add more boiling water if needed.
Wipe the rims of the jars clean. Centre the lids and screw the rings on fingertip tight.
Place the jars into your prepared pressure canner.
Close the canner and vent it according to your pressure canner's instructions before bringing it up to pressure.
Process pint jars for 25 minutes and quart jars for 30 minutes at the pressure required for your elevation and type of pressure canner.
Once the processing time is finished, turn off the heat and allow the canner to cool and depressurize naturally.
Carefully remove the jars and place them on a towel or cooling rack.
Leave the jars undisturbed at room temperature for 12 to 24 hours.
Check the seals. Remove the rings, label the jars and store them in a cool, dark place.