The article has a deeper reflection on the issue of metadata, that is, data which are defined or describe other data. The theoretical layer extracted three types of metadata: descriptive, structural, and administrative. Descriptive metadata is used to find and identify key information that allows the location of an object. Structured metadata describes the internal structure of the object, but administrative metadata refers to the technical information, where information is provided for example about the time and how the file was created. The purpose of the publication is to provide theoretical knowledge as well as practical. The second part of the article depicts the concepts of graphic and text files, and simple self-defense techniques are indicated, which allow you to remove metadata before sharing the file. The supplementing of article is: analysis the ability to extract meta information by Fingerprinting Organizations with Collected Archives (FOCA), which is used to mechanizedly extract metadata reflection on what the metadata includes the email header.