It seems like a good idea: an app that allows you to share your food and leftovers instead of throwing them away. Europe appears to think so.

Food-sharing apps have appeared in the United Kingdom, Germany, Greece, Hungary, Italy and the Netherlands, and are spreading across the rest of Europe. With most of them, you put your food online using the app, wait for someone to get in touch and then arrange for the food to change hands. (Where those hands have been, however, you may never know.)

Of course, before you buy, you need to know what’s cooking in someone else’s kitchen. Budapest-based app Piqniq can help satisfy that need. It allows users share what they are cooking and eating — and for users to share in those meals.

“With the use of Piqniq we are tearing down these walls with you, allowing us all to peek into each other’s kitchens and observe, discuss, exchange, taste or even buy food from one another.”

The app has about 2,000 members in Hungary, the United States, the United Kingdom, Australia and Germany and other countries, according to the Budapest Times.

Greece has Cookisto, which began as a way to connect home cooks with busy people looking for a hot meal. Founded in 2013 and expanded into the United Kingdom, Cookisto is described as a “community marketplace for homemade food.”

German Internet platform allows users to share surplus food in Germany, Austria and Switzerland. According to the Web site, which debuted in 2012, the app has more than 43,000 users who have saved 37,408 kilograms of food, which comes out to roughly 82,470 pounds.

Italian app Ratatouille allows users to post their extra food in their “fridge” in the app for others to claim and arrange drop-off points. The location-based app debuted for the iPhone in April and, according to the Ratatouille Twitter account, had nearly 300 users in May, including some in the United States. An Android app is in the works.

Back in the United States, LeftoverSwap, described as a “Craigslist for leftovers,” was developed in Seattle and began in 2013. Users take pictures of their offerings and post them for others to claim and pick up. Some of the guidelines for users include “Don’t give away any food that you wouldn’t eat yourself” and “Don’t take any food without knowing how old it is and making sure it was kept in proper storage.”

Worries are cropping up about regulation and the safety of food sharing. One food-sharing Web site in England, Casserole Club, requires members to take an online hygiene course and submit to a criminal record check before they are allowed to start cooking meals to share. Members cook extra portions of their meals to share with those unable to cook for themselves such as the elderly.

U.S. food regulations don’t apply to private citizens who share food through apps. Those worried about hygiene might pause before claiming a piece of leftover pizza or lasagna.

Consider: Did they leave it out too long? Did they need to follow the five-second rule? And where is that sneeze guard?