Material Replacer is an add-on that automates material management when merging or appending data between Blender files. It provides a batch replacement tool to update existing materials with newly appended versions, resolving naming conflicts like replacing 'mat' with 'mat.001' across a scene. The toolset includes a dedicated function to clean up and remove duplicate materials from the file, automatically reassigning the original base material to objects if it exists. Additionally, it offers a hide and restore feature that temporarily strips materials from all objects to improve viewport loading and draw times, while preserving the assignment data for rendering.