CAPTCHAs are tests designed to be easy for humans and hard for computers, and their roots go back to hackers of the 1980s and 1990s who wrote in leetspeak, swapping letters for look-alike symbols so keyword filters on forums would miss them. Commercial uses began around 2000, when idrive.com and PayPal used distorted text to block fraudulent sign-ups, asking people to retype words that software struggled to read. Google bought reCAPTCHA in 2009 and used the human answers to help digitize New York Times archives and Google Books. Later versions moved away from visible puzzles: they analyse user behaviour and device attributes, such as canvas fingerprinting, and show image challenges only to users judged high-risk.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.