OmniWeb is a discontinued web browser that was developed and marketed by The Omni Group exclusively for Apple's macOS operating system. Though a stable version is no longer maintained, it is still available as a free download and unstable versions are still being released.
OmniWeb was originally developed by Omni Group for the NeXTSTEP platform, and was released by Lighthouse Design on March 17, 1995 after only one month's development time. As NeXTSTEP evolved into OPENSTEP and then Mac OS X, OmniWeb was updated to run on these platforms. These early versions of OmniWeb also run on Microsoft Windows through the Yellow Box or the OpenStep frameworks. After Lighthouse Design was bought by Sun Microsystems, the Omni Group released the product themselves, from version 2.5 onwards. From version 4.0 onwards, OmniWeb was developed solely for the OS X platform.
OmniWeb was developed using the Cocoa API which allow it to take full advantage of OS X features. It uses Quartz to render images and smooth text. It makes use of multiple processors if available, and features an interface that made use of Aqua UI features such as drawers, sheets, and customizable toolbars.
The Omni Group originally employed its own proprietary HTML layout engine that use standard API NSText components. However, this engine was very slow, particularly when scrolling, and was not fully compatible with the most recent web standards, such as Cascading Style Sheets. In OmniWeb version 4.5, the Omni Group adopted Apple's KHTML-based WebCore rendering engine, which was created by Apple for its Safari browser.
On August 11, 2004, the Omni Group released version 5.0 of OmniWeb which added a number of new features. The most notable addition was an unusual implementation of tabbed browsing, in which the tabs are displayed vertically in a drawer on the side of the window (including optional thumbnail pictures of the pages.) Despite a certain amount of controversy over the merits of a tab drawer over a tab toolbar, the feature persists through the final version.