The Duolingo English Test (DET) is a standardized test of the English language designed to be internet-based rather than paper-based. The DET is an adaptive test that uses an algorithm to adapt the difficulty of the test to the test-taker. It was developed by Duolingo in 2014 as Test Center and grew in popularity and acceptance at universities during the COVID-19 pandemic. Ireland accepts the test as part of its student visa program. Some universities in the United Kingdom, such as the London School of Economics, Imperial College London, Kingston University, the University of Southampton, and Middlesex University, also accept the Duolingo English Test. Others, such as Oxford University, Cambridge University and Lancaster University do not currently accept the Duolingo English Test.