Choose a Speech Recognition Engine

Caster currently supports the following speech recognition engines on Microsoft Windows Vista through Windows 10. This is a brief overview of the supported speech recognition engines.

Dragon NaturallySpeaking

Dragon NaturallySpeaking (DPI) - Caster supports Dragon NaturallySpeaking 13 (DNS) or higher. For best results, Dragon Professional Individual (DPI) is recommended.

  • Known for its high accuracy in speech recognition especially with free dictation.

  • Has support from multiple accents and dialects

  • User Profile management and local vocabulary training

  • Polished GUI

  • Superior Background noise rejection. Distinguishes speech from background noise.


  • Closed source speech recognition engine
  • Expensive $300 DPI and Dragon NaturallySpeaking Home (DNS) $150 (Note DNS limitations below)
  • Will never have native cross-platform support by Nuance.
  • Cannot use custom speech recognition models
  • Zero low level access to the engine implementation

Dragon NaturallySpeaking Home (DNS) can be used by Caster however comes with significant limitations besides what's mentioned in their matrix comparison and therefore not recommended. The retail upgrade cost DPI is about the same as the Dragon NaturallySpeaking Home.

Limitations of the Home Edition include but not limited to:

  • Does not include vocabulary editor to edit/add/delete words for recognition.

  • Cannot add new DNS commands (You can add new commands created with Dragonfly)

  • Lacks built-in command/dictation/spell/number modes. Using command mode is recommended when programming by voice.

  • Lacks many other settings to customize DNS for productivity.


Daanzu's Kaldi open source engine cross-platform speech recognition based on Kaldi Project.

  • Free and open source engine that respects user privacy.

  • Typically lower recognition latency than DNS

  • A selection of pre-trained speech recognition models to choose from that are continually developed.

  • It's possible to use a data set with your own voice to train your own model if you have the necessarily technical skills and equipment.

  • Custom recognition weights for Grammar/Rule/Element

  • Low level access to speech engine and parameters that are customizable unlike DPI or WSR.

  • Optionally uses cloud-based machine learning to produce pronunciation's for unknown words

  • Alternative Dictation sources such as a cloud based or local speech recognition backend

  • Many other highlights can be found in Daanzu's Kaldi Documentation


  • Does not have a GUI for editing vocabulary (User Lexicon) but can be easily edited through txt file.
  • Currently does not support training the user lexicon speech recognition model locally.
  • Mileage may vary but typically free dictation accuracy is lower than DNS/DPI.

Windows Speech Recognition

Windows Speech Recognition (WSR) - Not Microsoft Cortana

  • Free

  • Simple to set up with the least dependencies

  • Preinstalled on all supported Windows OS


  • With Caster WSR built-in commands are not available and does not utilize WSR's GUI.

  • Least accurate with free dictation and commands

  • Not actively developed by Microsoft
  • Will never have native cross-platform support by Microsoft.
  • Cannot use custom speech recognition models
  • Zero low level access to the engine implementation