It was founded in 1982 by Günter and Reinhard Keil, initially as a German GbR.

In April 1985 the company was converted to Keil Elektronik GmbH to market add-on products for the development tools provided by many of the silicon vendors.

Keil implemented the first C compiler designed from the ground-up specifically for the 8051 microcontroller.

Keil provides a broad range of development tools like ANSI C compiler, macro assemblers, debuggers and simulators, linkers, IDE, library managers, real-time operating systems (currently RTX5)[1][2][3] and evaluation boards for over 8,500 devices.

[6][7][8] Since the merger with Arm, the company is still active in providing products and services.