The browser by Fenrir Inc. named for Odin’s eight-legged horse is Sleipnir.
Sleipnir is a tabbed browser developed by the Japanese company Fenrir Inc. Its name comes from Norse mythology, where Sleipnir is Odin’s eight-legged steed. The mythological name is especially fitting because Fenrir, the company’s name, is also taken from a creature in Norse mythology. The browser was originally created by Yasuyuki Kashiwagi.
Sleipnir became known for extensive tab customization, mouse gestures, page zooming, tab groups, and support for multiple layout engines. Early Windows versions could use Internet Explorer’s Trident engine or Mozilla’s Gecko engine; later releases added WebKit, and version 5 adopted Blink. The browser also appeared on platforms including Windows, macOS, Android, iOS, and Windows Phone at different points in its history.
The spelling matters: “Sleipnir” is the canonical name, while “Sleipner” is a variant seen in other contexts, including a Rudyard Kipling story. The browser’s name uses the mythological spelling ending in “-nir.”