Keil Product Downloads

or to check the status of your support and maintenance agreement. Further information about installing your software is available in the Read Me First brochure. Note For Flex Floating and user-based licenses (UBL) ， please use the PSN mentioned in Knowledgebase Article 2935. Refer to the Licensing User's Guide for setup instructions. ， XC166，。

XC2000 MCUs. Keil products use a License Management system - without a current license the product runs as a Lite/Evaluation edition with a few Limitations. Note Please note that these installers do not include protection against tampering. To help ensure the integrity of your Arm software installer， we recommend that installers be executed from a trusted directory that contains only the installer. Maintenance Status and Previous Versions Enter a valid Product Serial Number (PSN) or License Code (LIC) toget access to all product versions available to you， Select a product from the list below to download the latest version. MDK-Arm Version 5.43a (August 2025) Development environment for Cortex and Arm devices. C51 Version 9.61 (December 2022) Development tools for all 8051 devices. C251 Version 5.60 (May 2018) Development tools for all 80251 devices. C166 Version 7.57 (May 2018) Development tools for C166。