Panoramas were originally generated from Microsoft ICE http://bit.ly/msrice in 2008 and viewed offline or online via the HD View browser plugin http://bit.ly/msrhdview
In 2010, Photosynth.net added a panorama viewer which was not as high quality as HD View, but much easier for normal people to upload.
Later in 2010, the ICE team created a Photoshop plugin to publish panoramas to Photosynth.net http://bit.ly/pstops
In 2011, Photosynth released their first version of their mobile app, however mobile processing is not yet powerful enough to create photosynths, so only creates panoramas - and much poorer resolution panoramas than ICE or Photoshop.
In 2011, the Photosynth team also released the first basic version of an HTML5 panorama viewer which works on Internet Explorer 10+ and mobile Safari on iOS.