Wash cranberries and cook in water until soft. Press through a fine sieve for smooth sauce, or mash/leave whole for tested variations.
Add optional butter, stir in sugar, bring to a boil and boil 3 minutes.
Fill hot half-pint or pint jars, leaving 1/2-inch headspace; remove bubbles, adjust headspace, wipe rims and apply lids.
Process 15/20/20/25 minutes at 0–1,000/1,001–3,000/3,001–6,000/above 6,000 ft.