Enrichr is an interactive and collaborative web-based and mobile application designed for gene list enrichment analysis. It includes new gene-set libraries, an alternative ranking method for enriched terms, and various interactive visualizations using the D3 JavaScript library. The software can be embedded into any tool that performs gene list analysis. Enrichr was evaluated by comparing the enrichment signatures of nine cancer cell lines to those of matched normal tissues, revealing common patterns such as up-regulation of the polycomb group PRC2 and enrichment for the histone mark H3K27me3 in many cancer cell lines. Additionally, it showed alterations in Toll-like receptor and interleukin signaling in K562 cells compared to normal myeloid CD33+ cells. Enrichr provides various visualization options, including bar graphs, tables, grids, and networks, and allows users to share results with collaborators. The software is open-source and freely available online at http://amp.pharm.mssm.edu/Enrichr.Enrichr is an interactive and collaborative web-based and mobile application designed for gene list enrichment analysis. It includes new gene-set libraries, an alternative ranking method for enriched terms, and various interactive visualizations using the D3 JavaScript library. The software can be embedded into any tool that performs gene list analysis. Enrichr was evaluated by comparing the enrichment signatures of nine cancer cell lines to those of matched normal tissues, revealing common patterns such as up-regulation of the polycomb group PRC2 and enrichment for the histone mark H3K27me3 in many cancer cell lines. Additionally, it showed alterations in Toll-like receptor and interleukin signaling in K562 cells compared to normal myeloid CD33+ cells. Enrichr provides various visualization options, including bar graphs, tables, grids, and networks, and allows users to share results with collaborators. The software is open-source and freely available online at http://amp.pharm.mssm.edu/Enrichr.