Substitutes for Jell-o in a recipe include gelatin alternatives such as agar-agar or carageen. Other options include products that perform similarly to Jell-o, but aren't animal-based, making them acceptable for vegans to use. Examples include kosher gelatin and Vegan Jel, made by Natural Desserts.
Agar-agar, which is made from pressed seaweed, can typically be found in bar, powder or flake form. Grinding the agar-agar in a price mill creates a fine powder that can be substituted equally for Jell-o. Carrageen is also derived from seaweed. Using carrageen in place of Jell-o involves rinsing the whole, dried seaweed and soaking it in water for 12 hours before boiling it with whatever liquid the recipe calls for. For each 1 cup of liquid, 1 ounce of dried carrageen is required.