An IE shell called Netcaptor was the first browser to implement tabs, back in 1997. I used it myself until Phoenix (nee Firefox) released a couple years later.

An IE shell called Netcaptor was the first browser to implement tabs, back in 1997. I used it myself until Phoenix (nee Firefox) released a couple years later. Contrary to what this silly site says, MDI windows are not by any stretch of the imagination _tabs_.