Is the online domain really so terribly important for drug policy researchers to engage with in order to study drugs and drug policy? Is illicit drug use not, after all, an ‘offline’ activity enacted by people with their offline identities as they buy, sell and consume – not digital – but physical psychoactive substances? With this special section of International Journal of Drug Policy, we aim to persuade readers of the importance of the internet and other digital technologies in generating research aimed at understanding the people who use illicit drugs, in understanding illicit drug supply, and for devising and evaluating effective drug policies. In doing so, we introduce a series of articles by researchers using online data and methods that enable them to gain fresh drug policy-relevant insights. Many of these insights, we argue, would not otherwise be possible using traditional research methods and data sources. All articles from this special section originated from presentations made at the 12th annual conference of the International Society for the Study of Drug Policy (ISSDP) held in Vancouver, in May 2018.