FreeTDS is a free implementation of the TDS (Tabular Data Stream) protocol that is used by Sybase and Microsoft for their database products. It implements TDS 4.2, 5.0, 7.0 and 8.0, and can communicate with any Sybase or Microsoft SQL Server.

FreeTDS comes with a low level library (the TDS layer) along with a number of APIs (Application Programming Interfaces). The APIs are DB-Lib, CT-Lib, and ODBC.

FreeTDS has many possible uses. It has been used by Unix/Linux webservers to present data stored in SQL Server to the web, to port SQL Server database code from NT to Unix, to import data into SQL Server from a Unix source, and to provide database access on platforms (such as realtime systems) that have no native drivers.

The FreeTDS C libraries are available under the terms of the GNU LGPL license, consult the COPYING.LIB file in the distribution for details.