WorldWide Telescope (WWT) is an open-source set of applications, data and cloud services,[4][5] originally created by Microsoft Research but now an open source project hosted on GitHub.

Users are able to navigate the sky by panning and zooming, or explore the 3D universe from the surface of Earth to past the Cosmic microwave background (CMB), viewing both visual imagery and scientific data (academic papers, etc.)

WWT is completely free and currently comes in two versions: a native application that runs under Microsoft Windows[9] (this version can use the specialized capabilities of a computer graphics card to render up to a half million data points), and a web client based on HTML5 and WebGL.

"[14] As of February 2012 the earth science applications of WWT are showcased and supported by the Layerscape community collaboration website, also created by Microsoft Research.

The Earth mode has a default data set with near global coverage and resolution down to sub-meter in high-population centers.

Unlike most Earth viewers, WorldWide Telescope supports many different map projections including Mercator, Equirectangular and Tessellated Octahedral Adaptive Subdivision Transform (TOAST).

There are also map layers for seasonal, night, streets, hybrid and science oriented Moderate-Resolution Imaging Spectroradiometer (MODIS) imagery.

Other bodies, spacecraft and orbital reference frames can be added and visualized in the Solar System Mode using the layer manager.

Reference frames can contain orbital information allowing 3d models or other data to be plotted at their correct location over time.

Using ASCOM the user can connect a computer-controlled telescope or an astronomical pointing device such as Meade's MySky, and then either control or follow it.

[11] WorldWide Telescope contains a multimedia authoring environment that allows users or educators to create tours with a simple slide-based paradigm.

Pictures, objects, and text can be added to the slides, and tours can have both background music and voice-overs with separate volume control.

[11] The WorldWide Telescope was designed to be the embodiment of a rich virtual observatory client envisioned by Turing Award winner Jim Gray and JHU astrophysicist and co-principal investigator for the US National Virtual Observatory, Alex Szalay in their paper titled "The WorldWide Telescope".

This allows using consumer DLP projectors to create a projection system with resolution, performance and functionality comparable to high-end turnkey solutions, at a fraction of the cost.

[17] WorldWide Telescope was praised before its announcement in a post by blogger Robert Scoble, who said the demo had made him cry.

"[19] Dr. Roy Gould of the Center for Astrophysics | Harvard & Smithsonian said: A PC World review of the original beta concluded that WorldWide Telescope "has a few shortcomings" but "is a phenomenal resource for enthusiasts, students, and teachers.