WorldWideWeb, later renamed to Nexus to avoid confusion between the software and the World Wide Web, was the first ever web browser and editor. Tim Berners-Lee, who invented the World Wide Web together with Robert Cailliau, built the first working prototype in late 1990 and early 1991. That first prototype consisted of a web browser for the NeXTStep operating system. This first web browser, which was named “WorldWideWeb,” had a graphical user interface and would be recognizable to most people today as a web browser. However, WorldWideWeb did not support graphics embedded in pages when it was first released.
You can learn more about the original “WorldWideWeb” browser from Tim Berners-Lee himself.