About NVDA

General Features

Providing feedback via synthetic speech and Braille, NVDA allows blind and vision impaired people to access and interact with the Windows operating system and many third party applications.

Major highlights include:

  • Ability to run entirely from a USB stick or other portable media without the need for installation
  • Browsing the web with  Mozilla Firefox 3
  • Easy to use talking installer
  • Working with email using  Mozilla Thunderbird 3
  • Support for Microsoft Internet Explorer
  • Basic support for Microsoft Outlook Express / Windows Mail
  • Basic support for Microsoft Word and Excel
  • Support for accessible Java applications
  • Support for Adobe Reader
  • Early support for IBM Lotus Symphony
  • support for Windows Command Prompt and console applications
  • Automatic announcement of text under the mouse and optional audible indication of the mouse position
  • Support for many refreshable Braille displays

Internationalization

It is important that people anywhere in the world, no matter what language they speak, get the same access to technologies. NVDA currently has been translated into over 20 languages including: Brazilian Portuguese, Czech, Finnish, French, German, Hungarian, Italian, Portuguese, Slovak, Spanish, Swedish, Traditional Chinese, Vietnamese, Afrikaans, Galician, Croatian, Japanese, Polish, Russian, Thai and Ukrainian.

Speech Synthesizer Support

Apart from providing its messages and interface in several languages, NVDA can also enable the user to read content in any language, as long as they have a speech synthesizer that can speak that language.

NVDA is bundled with  eSpeak, a free, open-source, multi-lingual speech synthesizer. Additionally, NVDA can use both SAPI4 and SAPI5 speech engines to provide speech output.

Innovation and Experimentation

NVDA is not driven by profit, nor is it constrained by a need to follow market trends and demands. This allows for the freedom to research, experiment with and implement new, innovative techniques to improve accessibility for blind and vision impaired users, as well as enabling features desirable to minorities to be given higher priority where appropriate.

System Requirements

NVDA runs on both 32-bit and 64-bit editions of Microsoft Windows XP or later. Although not officially supported or tested, success has also been reported running on Windows 2000. NVDA has no additional hardware requirements beyond those of the operating system and requires less than 50 mb of disk space.

Technical Design and Implementation

NVDA is written in the  Python programming language, which allows for rapid development among other benefits. Code that needs to be injected into other processes is written in C++ for high performance. NVDA is built with an extensible, modular, object oriented, abstract design. Its code can be easily extended in order to support new applications and controls. App Modules can be written to add overall support for a specific application, virtual buffers can be written to allow NVDA to display complex documents or other data, and NVDA Objects can be written to add support for specific controls or Windows. NVDA's abstract design allows for the seemless support and integration of many different accessibility and native APIs. It is designed with a focus on accuracy, efficiency and optimisation.

For a detailed overview of NVDA's technical design, see DesignOverview.

Licence and Copyright

NVDA is copyright © 2006-2009 NVDA contributors.

NVDA is covered by the GNU General Public License (Version 2). You are free to share or change this software in any way you like as long as you distribute the licence along with the software, and make all source code available to anyone who wants it. This applies to both original and modified copies of the software, plus any software that uses code taken from this software.

For further details, you can  view the full licence.