'Waste not, want not' might be an old adage, but it's more important now than ever. Globally, we throw away around 1.3 billion tonnes of food every year. Apps like Too Good To Go, Olio and Karma all hope to make a dent in that pile of waste.
While some of the food waste we generate has to go in the bin - the mouldy carrots hiding at the back of your fridge, for example - plenty of the food we throw away is perfectly edible. Food waste apps connect users with restaurants, cafes and shops that end the day with leftovers that they can't sell, and would otherwise go to landfill.
Why bother? Not only does mass food waste put enormous strain on natural resources, but it also generates greenhouse gas emissions. If food waste were a country, it would be the third biggest global emitter of greenhouse gas - that's six times as much as the aviation industry.
To find out how useful these apps are in practice, video reporter Harry Kind spent an entire week eating nothing but food waste. Watch the full video above to see his verdict and decide whether you'd like to give them a go.
These are usually advertised as being about a third of their full value but prices can vary, often in the customers favour. The catch is: you don't usually know what food you'll actually get in the 'Magic Bag' before you pay for it over the app and collect it from the retailer.
The app covers most of the big coffee chains: Caffe Nero, Costa, Starbucks and Pret all are listed, as well as Greggs, Morrissons and hundreds of independent businesses.
Watch the video above to see how it worked for Harry.
It's free to download, and you pay for the products you order over the app and then collect them from the store.
It doesn't have nearly the range as Too Good To Go, so you're likely to have limited choices if you're outside London.
Find out more in the video above.
Its remit is larger than the other two apps, which only focus on food waste. Olio users can list and collect both food and non-food items in three sections.
The first is for free giveaways of both food and non-food items by local individuals or businesses (called 'Food Heros'), the second is for borrowing items listed by neighbours and the third, called Olio Made, is set up for local makers to sell homemade crafts and food products.
Harry found that a lot of his nearby food listings were donated by Tesco at the end of the day. In the evenings, volunteers at the supermarket listed products that would otherwise go to waste, which app users snapped up and collected the next day.
Because the grocery products were at or past their best before dates, he found he needed to make quick use of them.
Watch the video above to get our full verdict.