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Download Products

Select a product from the list below to download the latest version.

MDK-Arm Download MDK-Arm
Version 5.40 (May 2024)
Development environment for Cortex and Arm devices.
C51 Download C51
Version 9.61 (December 2022)
Development tools for all 8051 devices.
C251 Download C251
Version 5.60 (May 2018)
Development tools for all 80251 devices.
C166 Download C166
Version 7.57 (May 2018)
Development tools for C166, 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.

Maintenance Status and Previous Versions

Enter a valid Product Serial Number (PSN) or License Code (LIC) to get access to all product versions available to you, 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.


For Flex Floating licenses, please use the PSN mentioned in Knowledgebase Article 3698. Refer to the FlexLM Client Setup Guide for setup instructions.

Notes Note

  • Use a current Product Serial Number (PSN) to get a License Code (LIC) that converts the Lite/Evaluation version to a full edition
  • Evaluation editions of Keil software products do not require a Product Serial Number or License Code.
  • Vendor specific toolkits should be downloaded from
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