Fast UniFrac is a new version of UniFrac that is specifically designed to handle very large datasets. Like UniFrac, Fast UniFrac provides a suite of tools for the comparison of microbial communities using phylogenetic information. It takes as input a single phylogenetic tree that contains sequences derived from at least three different environmental samples, a file mapping ids used in the tree to a set of unique sample ids (same format as prior version 'environment file', and an (optional) category mapping file describing additional relationships between samples and subcategories for visualizations. For example, in a given set of gut samples, you might define subcategories for different diets, different physical locations/dates, different species, and/or different treatments like antibiotics or high fat. For sample data click here. For citation, click here.

Both the UniFrac distance metric and the P test can be used to make comparisons. Both of these techniques bypass the need to choose operational taxonomic units (OTUs) based on sequence divergence prior to analysis, although for large datasets, this is still recommended in order to reduce the computation power needed to conduct the analysis.

Fast UniFrac allows you to:

• Determine if the samples in the input phylogenetic tree have significantly different microbial communities.
• Cluster samples to determine whether there are environmental factors (such as temperature, pH, or salinity) that group communities together.
• Determine whether system under study was sampled sufficiently to support cluster nodes.
• Easily visualize the differences between samples graphically, with support for three dimensional exploration of datasets and with multiple subcategory coloring.

Please enter your email and password to continue. After you register you will be able to analyze up to 100000 unique sequences, up to 200 samples, and perform significance test based on up to 1000 tree permutations. Please note that if you are already registered for the original UniFrac web interface, you will need to e-mail MicrobiomeHelp@colorado.edu in order to register for fast unifrac. We apologize for the inconvenience.

If you do not wish to register, you can analyze up to 50000 unique sequences, up to 100 samples, and perform significance test based on up to 10 tree permutations using the guest account. The guest account email is guest and the password is guest.

If you wish to analyze much larger datasets than the defaults, please contact us and we will be happy to try to accommodate you.

NOTICE: it has come to our attention that for analyses run before June 3rd, 2010, unweighted UniFrac analysis returned the results of a normalized weighted UniFrac analysis if performed immediately after a normalized weighted analysis in the same web browser session. This bug did not affect the non-normalized, weighted option and applies to PCoA, Cluster Samples, Sample Distance Matrix, Jackknife Cluster Samples, and UniFrac Significance. We apologize for this error and thank Mircea Podar for drawing it to our attention.

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