While false rumours, inaccurate reporting, and conspiracy theories have existed for as long as there were people to create and spread them, the Internet has reshaped and amplified the ability to produce and perpetuate false and misleading content. Stopping the creators and spreaders of untruths online is essential to reducing political polarisation, building public trust in democratic institutions, improving public health, and more generally improving the wellbeing of people and society. This Going Digital Toolkit note discusses the importance of access to accurate information online and presents a novel typology of the different types of untruths that circulate on the Internet. It considers how untruths are spread online as well as the consequences, and it surveys the evidence base of false and misleading information online. The note concludes by identifying approaches to fighting untruths online and mitigating their negative effects.