Ah, I see, thanks Jeremy. I did see the html entry in the datatypes_conf.xml, but (erroneously) thought that I was to use the datatype listed after the colon ("Html") rather than the extension (which is "html"). <datatype extension="html" type="galaxy.datatypes.images:Html" mimetype="text/html"/> Setting my output type to "html" produces the desired behavior. Thanks again, -- Jay On Feb 4, 2013, at 10:16 AM, Jeremy Goecks wrote: My outputs section in the tool's xml file is: <outputs> <data format="HTML" name="fred_report" label="generating FRED report..."/> </outputs> You should set the output format to 'html' — all lower case. Galaxy has a list of known dataset types in datatypes.conf, and your output format should always match one of those in the file. Finally, please always include the mailing list in your reply so that emails are tracked and archived. Best, J.