I have an FBX that includes animation. I must use the Legacy Rig type (this requirement is beyond my control). I need to edit animation curves, which legacy animation doesn't support (as far as I know). To do this, I have to roll out my FBX in the Project view, select the animation, and duplicate it, to create a write-able copy of the animation in my Unity project, in the form of a *.anim file. If I make any edit to the extracted .anim file, even if it's something very small like moving a single keyframe, the .anim file size balloons, like 4x - 20x the size of the un-edited .anim file. Does anyone know if there's a way to prevent this? An acceptable workaround would be if there's a way to edit curves of an animation within an FBX, with Rig type set to Legacy, but as far as I know that's not possible. I suppose this huge file size would also be acceptable if anyone can guarantee that it does not impact the file size of a build for the end user. I have used various mesh compression settings and animation compression settings in the FBX import settings. Higher compression does result in smaller file size when I extract the .anim file. But the file size still balloon once I make any edits. What I edit or how much I edit doesn't seem to matter - the file size always jumps to (nearly) the same size (within maybe 0.1%). In case anyone is trying to reproduce this, the reported file size in Windows does not actually update until/unless I close the Animation window in Unity AND click "Save project." (Or quit Unity, presumably). Thank you!