The program Claxa is intended for tracking an object in a video footage constructing the mask of the object and subsequent extraction of the object. Tracking an object with the aim to extract it means precise detection of its boundaries on a pixel level. In this relation Claxa admits much more alive and natural movements of the mask even more believable than manual construction of the mask using Bezier-spline in Adobe After Effects (AE) because the mask receives many more degrees of freedom and it can reproduce the finest movements of the object which are beyond the reach of human operator. Except binary masks where each pixel is unambiguously attributed to the object or to background Claxa can build smooth raster masks with soft transition from background to foreground. By the description this feature resembles well known feather from many graphics packages but in Claxa smoothing of the boundaries depends not only on geometrical distance from the center of the object-background transition but also on real spread of the boundary in the given place of the current frame.Claxa offers several options for masks built in it to be subsequently processed in AE. Here are the export types:1) Source footage with everything erased (or replaced with data from another footage) except for the object. 2) Sequence of masks for each frame from the source footage. 3) Approximate description of the mask in the form of dynamic B-spline which can be exported in AE layer as ordinary mask with the possibility to edit it by hands and apply additional effects to it in AE.Technically the tracking in Claxa is performed by comparison of the frame where a user has drawn static mask for reference with the rest frames of some part of the footage on the base of colors coincidence and evenness of boundaries transformation.