POSTAR2 is a comprehensive database for exploring post transcriptional regulation based on CLIP seq data, Ribo seq data, RNA seq data and other high throughput sequencing data from 6 species, including human, mouse, fly, worm, Arabidopsis, and yeast. POSTAR2 is developed as the updated version of CLIPdb and POSTAR, which provides the largest collection of RBP binding sites and functional annotations.