Characterizing vaping posts on instagram by using unsupervised machine learning.

•Prevalence of photos in online spaces make them highly engaging.•Large-scale analysis of substance-use images remain limited so far.•We use machine-learning methods to study #Vaping images on Instagram.•Most of the images depicted e-liquids, e-cigarettes or vaporizers, and selfies.•Instagram is widely used to promote vaping products to the youth.