Digital contents watermarking Piracy of digital contents is a real and substantive problem. The watermark technique has received attention as one of solutions for the threat, because it hides some information for copyright protection into the digital content. And once the content is illegally copied, the watermark is detected from the copied one and used as an evidence of piracy. In this presentation, an overview of the image watermark technique is presented. Besides, various attacks to the watermark are also introduced to show that the watermark technique is still a young and an emerging research area. Then, some matters encountered in the practical use are discussed.