QR Code encoder in Erlang
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QR Code Encoder

Reference used was ISO/IEC 18004, 1st Edition (2000)

This implementation is informed by my specific needs, i.e. to provide two-factor authentication for mobile phones running Google Authenticator.

  • "Byte" mode only (don't need e.g. numeric mode or kanji mode).
  • Encode only (no detection/decode).
  • Basic supporting library functions provided (HOTP, PNG image functions) to allow full-cyle demo.


  1. Download repo and compile with erl -make
  2. Install Google Authenticator App on your mobile:
  3. Run demo: qrcode_demo:run().
  4. Open the generated qrcode.png file
  5. Scan the qrcode into the phone.
  6. Ensure server clock is correct.
  7. The value of qrcode_demo:totp() should show the same passcode as the phone.
  8. Handle PINs/logins for the second part of the "two factor" according to your application design.

NOTE: This documentation is rather basic as this was open-sourced by specific request!