Which browser did Microsoft license from Spyglass to create Internet Explorer 1.0?

Microsoft licensed Spyglass Mosaic from Spyglass to create Internet Explorer 1.0. Spyglass Mosaic was a commercial browser with formal ties to the earlier NCSA Mosaic project, but it was Spyglass—not NCSA—that licensed the software to Microsoft.

Microsoft began its Internet Explorer project in 1994 as the web rapidly gained popularity. Spyglass supplied Microsoft with Mosaic technology, and Microsoft modified it for Windows. The first Internet Explorer release appeared in August 1995 as part of the Microsoft Plus! add-on for Windows 95.

A common mix-up is answering “NCSA Mosaic.” NCSA created the pioneering Mosaic browser, while Spyglass commercialized Mosaic-related technology and acted as Microsoft’s licensing partner. Internet Explorer was therefore derived from Spyglass Mosaic, even though the two projects were historically connected.

Microsoft’s licensing arrangement later became controversial. Because Internet Explorer was bundled with Windows rather than sold separately, Spyglass argued that Microsoft had avoided expected royalties; the dispute ended in a reported $8 million settlement in 1997.