The image format developed as a patent-free alternative to GIF was PNG, or Portable Network Graphics. PNG emerged in 1995 after controversy over the patents covering GIF's LZW compression method.
GIF had become widely used on the early web, but Unisys asserted rights connected to LZW and sought licensing arrangements from software developers and commercial users. That situation encouraged developers to create an openly implementable format that would avoid the patent issue. PNG was designed for lossless compression, broad color support, and reliable transparency.
PNG improved on GIF in several important areas. It supports indexed images as well as 24-bit truecolor and alpha transparency, while ordinary GIF uses a palette of up to 256 colors and traditionally has only one transparent palette index. PNG's major historical weakness was animation: the original format did not provide GIF-style animation, although APNG later extended PNG for that purpose.
The relevant GIF patents eventually expired, but PNG remained an important format for graphics, screenshots, logos, and images requiring transparency.