Glide was a proprietary 3D graphics API developed by 3dfx used on their Voodoo graphics cards. It was dedicated to gaming performance, supporting geometry and texture mapping primarily, in data formats identical to those used internally in their cards. The Voodoo cards were the first to offer performance to really make 3D games work well, and Glide became fairly widely used as a result. The introduction of DirectX and full OpenGL implementations from other vendors eventually doomed Glide, and 3dfx along with it.

Glide is based on the basic geometry and "world view" of OpenGL. OpenGL is a very large library with about 250 calls in the API, many of which are of limited use. Glide was an effort to select those features that were truly useful for gaming, leaving the rest out. The result was an API that was small enough to be implemented entirely in hardware. That hardware, of course, was 3dfx's own Voodoo cards. This led to several odd limitations in Glide, for instance it only supported 16-bit color.

The combination of the Voodoo's raw performance and Glide's easy-to-use API resulted in Voodoo cards generally dominating the gaming market from the mid to late 1990s. The name Glide was chosen to be indicative of the GL underpinnings, while being different enough to avoid copyright problems. 3dfx also supported a low-level MiniGL driver, making their cards particularly popular for players of the various Quake-derived games. MiniGL was essentially a "different Glide" with a wider selection of OpenGL calls and lacking the dedication to a single hardware platform. Due to the Voodoo's "GL-like" hardware, MiniGL on Voodoo was very "thin" and ran almost as well as Glide.

As new cards entered the market 3dfx managed to hold the performance crown for a short time, based largely on the tight integration between Glide and their hardware. This allowed them to be somewhat lax in hardware terms, which was important as the small gamer-only market 3dfx sold into wasn't large enough to support a large development effort. It was not long before offerings from nVidia and ATI Technologies were able to outperform the latest Voodoo's using standard APIs. 3dfx responded by releasing Glide as an open-source API, but it was too late, by late 1999 when they announced it almost all games had long since moved to Direct3D, or a smaller number to OpenGL.