Freerice

Freerice is an ad-supported, free-to-play website and mobile application that allows players to donate rice to families in need by playing a multiple-choice quiz game. For every question the user answers correctly, ten grains of rice is donated via the United Nation's World Food Programme.
The available categories include Global Goals: Using Facts to Fuel Action, English, Geography, Humanities, Language Learning, Math, and Science. The categories encompass a total of 24 diverse subjects that can be played on up to five difficulty levels, depending on the subject. A user's total score is displayed as a mound of rice and number of grains earned.
History.
The website went live on October 7, 2007, with 830 grains of rice donated on its first day. The site was created by John Breen, a computer programmer, to help his son study for the SAT exam. The second word in its name was originally capitalized as "FreeRice". On November 20, 2007, the WFP launched a campaign to "feed a child for Thanksgiving", encouraging internet users "to take time out from traditionally the busiest online shopping period of the year and help the hungry" by playing the game. For a brief while, the amount of rice donated per correct answer was increased to 20 grains, though this was reduced to 10 grains of rice per answer within a few months. Since July 30, 2020, it has been temporarily reduced to 5 grains and later 1 due to a collapse in the advertising market from the COVID-19 pandemic.
In March 2009, Breen donated the FreeRice website to the World Food Programme.
Freerice 2.0 launch.
In September 2010, the UN World Food Programme launched a new version of the game with social networking, groups, rankings and achievements. As part of the launch, the site dropped the second capitalization in its name, going from "FreeRice" to "Freerice".
Freerice Beta Launch.
In August 2018, the UN World Food Programme launched a newer, more improved version of the game on a new website. The beta has a new interface and is mobile-friendly. Apps for iOS and Android have also been released with this version of the website.
Versions in other languages.
In 2011, Freerice launched new language versions of the website in Spanish, French, Italian, Chinese and Korean, allowing users to play the popular game across a number of subjects in their own language for the first time. Freerice China is currently offline, as the World Food Programme has ended its contract with the partner responsible for building and maintaining it.
Leaderboards.
Freerice users can see the total rice they donated, as well as their current ranking on the site. The website also allows creating groups, of which players can join using a group code. The group score is determined by the total rice donated by the group members while they are a part of the group. The website publicly displays two leaderboards of the top 50 individuals and top 50 groups, along with the scores of each.
Effectiveness.
In its first ten months of operation, Freerice donated over 42 billion grains of rice. One month after the inception of the viral marketing program, users had earned enough points for one billion grains of rice. The United Nations' World Food Program stated that this amount could feed 50,000 people for one day, since it takes 400 grams or about 19,200 grains of rice to feed one adult for a day. Using this calculation, enough rice was donated in 2008 to feed over 6,000 people daily for each day of that year. Since its inception, as of April 3, 2013, Freerice players had earned sufficient rice for over 10 million meals, assuming 2 meals per day.
Monthly count.
Total All Dates (as of August 2014): 102,819,312,476 
Modified data as of April 30, 2021: 101,809,095,196.
References.
Glitch notes.
Freerice glitched in late December 2015, and the yearly total became a negative number, thus subtracting the year's totals from the aggregate total. The problem has reappeared in 2015 and 2016, so the issue appear to be with 32-bit signed binary integers counting the grains. This explains why the displayed total is so much lower than the true total.