Clean and sterilize canning jars according to manufacturer's directions.

Finely chop the bell peppers and jalapeños in a food processor fitted with the blade attachment or using the fine shredder attachment, or finely chop the peppers by hand. Drain excess liquid from the peppers before proceeding (this helps ensure the jelly will set up).

For liquid pectin: to a 5- or 6-quart pot, add the peppers, vinegar, salt and sugar. Bring the mixture to a boil for 5 to 10 minutes, stirring often.

Add the liquid pectin and boil at a rolling boil (that can't be stirred down) for 1 more minute. Remove the pot from the heat.

For powdered pectin: to a 5- or 6-quart pot, add the peppers, vinegar, salt and powdered pectin. Bring the mixture to a boil for 1 minute.

Add the sugar and bring to a boil again, stirring constantly. Boil at a rolling boil (that can't be stirred down) for 1 full minute. Remove the pot from the heat.

Pour jelly to within ¼-inch of the top of prepared canning jars. Wipe the rim of the jar with a clean rag. Place a lid and ring on each jar.

Process in a water bath or steam bath canner for 10 minutes adding additional time for elevation, if needed (see note).

Remove from the canner and let sit on the counter until fully cooled and lids have popped/sealed.