An unopened packet of ketchup is OK to use for one to two years after the expiration date printed on the packet. Expiration information is labeled as a "best by" or "use by" date.
Tomato ketchup is a popular condiment for foods such as hamburgers, french fries and hot dogs. Small ketchup packets are available at restaurants and fast food establishments. Generally, ketchup packets remain good for up to a year after the printed expiration date.
The vinegar and tomatoes in ketchup make it acidic, which allows it to stay fresh longer. Ketchup that is no longer safe to eat turns to a dark maroon color with a thick consistency.