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Why Zemu?

Integration and end-to-end testing of Ledger Apps is a manual and time consuming process. We believe that the Ledger apps ecosystem is lacking an adequate approach with respect to testing. The Zemu Framework is our solution for this problem. We stand on the shoulders of the giant greenknot’s speculos.

It's currently being used in every Ledger App built by Zondax, among many others (such as Ethereum one built by Ledger team).

Zemu is an emulation and testing framework for Ledger Nano S/S+/X devices


  • Minimal configuration + Docker based
  • Speculos/Qemu based emulation
  • Easy JS API
    • Mocha / Jest compatible
    • Abstracted device control (buttons, reset, etc.)
    • Navigate thru screens and take screenshots of them
  • Debugging (support for CLion and vscode, even mixed C/Rust)
  • Minimal configuration + Docker based

Who we are?

We are Zondax, a company pioneering blockchain services. If you want to know more about us, please visit us at