Why are IK bones exported?

I have rigged my character using Rigify. I have created an animation, and in the dope sheet I only have channels for the regular bones:

Now, when I export the character to FBX, it takes the IK bones with it. Even more strange: the animation tracks are tied to the IK bones, and not to the regular bones as is shown in the dope sheet.

I want my object to be as clean as possible.

When you export an FBX, by default it will export ALL the bones. There is an option so that you only export deform bones…

image

As for it putting animation on the IK bones… you know that on the rigify rig, the FK bones are not actually the deform bones? Could it be that this is what is going on? This won’t be a problem - when you export to FBX, all the actions are baked to a keyframe every frame, for every bone.

Ah, that’s much better!

But now on all channels that actually do something, there is a keyframe for every frame… as if Blender had done the interpolation already…

And when loading the model in ThreeJS I now have some issues with what looks like some unwanted scaling and rotation only when I play the animation (the non animated model is ok)