Dogs can technically eat plain, unflavored gelatin safely in moderation, but they should not eat Jello that contains sugar, artificial flavors, or sweeteners like xylitol, which can be toxic to dogs. Commercial Jello is not safe for dogs because of its high sugar content, artificial ingredients, and sometimes toxic sweeteners. Plain gelatin offers no nutritional value and may cause mild digestive issues but does not pose the same risks as flavored and sweetened Jello. Homemade dog-friendly gelatin treats made with plain gelatin can be a safer alternative. Overall, it's best to avoid giving dogs regular Jello and instead offer healthy, dog-appropriate snacks.