The analysis of binary data remains a challenge, especially for large or potentially inconsistent files. Traditionally, hex editors only make limited use of semantic information available to the user. We present an editor that supports user-supplied semantic data definitions. This semantic information is used throughout the program to realize semantic data visualization and data exploration capabilities not present in similar systems. Visualization and human-computer interaction techniques are applied. We show that this makes recognizing the structure of unknown or inconsistent data much more effective. Our approach demonstrates concepts that can be applied to the visual analysis of raw data in general.