In 2011 we introduced track data hubs (26), a means for users to import collections of their own locally hosted genome annotations into the Genome Browser where they may be organized, configured and viewed alongside native tracks. Track hubs now support four compressed binary indexed file formats: BigBed and BigWig (27), both developed at UCSC, BAM (28) and VCF/tabix (29). As genome sequencing becomes more accessible and cost-effective, we have faced a growing demand from researchers who wish to use the Genome Browser tools to browse and annotate genome sequences for which we do not host a database. In response to this need, we have extended the functionality of track data hubs to encompass entire assemblies that are not hosted natively on the Genome Browser. These ‘assembly data hubs’ enable researchers to import both the underlying reference sequence as well as data tracks annotating that sequence into the Genome Browser for display and analysis. The genome sequence is stored in the UCSC .2bit format and made available on the user’s remote web server, along with optional annotation data files stored
