The game, which went online in early October, tests the vocabulary of participants. Each time an internet user clicks on a correct answer, the website donates money to purchase 10 grains of rice.
So far, the game has raised one billion grains of rice, which is enough rice to feed 50,000 people for one day, the WFP said. "FreeRice really hits home how the web can be harnessed to raise awareness and funds for he world's number one emergency," the BBC quoted WFP head Josette Sheeran as saying.
She revealed that the existence of the game spread with the help of internet bloggers and websites like Facebook and YouTube.
"The site is a viral marketing success story," she said.
US online fundraising pioneer John Breen is behind the invention of FreeRice.