Web Slices are a web feed technology based on the hAtom Microformat that allows users to subscribe to portions of a web page. Microsoft developed the Web Slice format, and published a specification under their Open Specification Promise. The specification is not published by any independent standards body. Introduced in Internet Explorer 8 Beta 1, Web Slices can be previewed in a fly-out window. As of 2012,[update] Internet Explorer 8 and 9 were the only browsers to support Web Slices natively, although Mozilla Firefox had support via an add-on called webchunks.