The 'LeftoverSwap' app allows users to snap a photo of their uneaten food, add a food description and post it. Those looking to find cheap food can tap the "Map" section in the app and zoom in to their area to find if anyone posted food.
Tapping a green pin gives a small preview of the food. If users want to grab the food, they can hit contact to start a conversation and organise a way to meet up with the seller.
"Leftover Swappers don't feel the need to eat an enormous restaurant portion, and instead pass it on to a hungrier neighbour, in turn learning their name and avoiding excess calories," according to the app's website. However, the app has raised some health concerns.

Leftovers are one of the main sources of food poisoning, even when people stick to their own second-day dinners. Gustatory hand-me-downs from strangers are even more dangerous, according to 'LiveScience'.

"There would be no way for officials to trace the source, they wouldn't know who originally produced the food and under what conditions," San Francisco health department environmental regulatory programme director Richard Lee told 'SF Weekly' when the app first surfaced in July.

"Even if it came from the cleanest, best-inspected restaurant in San Francisco, it could still have been handled by some grubby hipster with no hygiene standards," Lee said.