Renormalize
Resizing a normal map, blurring it, blending it in an image editor or saving it through a lossy format all weaken the map. The surface then lights as if it were partly flat, so the whole thing looks washed out and the highlights go soft.
This scales every pixel back up to full strength while leaving the direction it points alone. It is the standard cleanup pass after anything touched a normal map without knowing it was one.
When do I need this?
After scaling a normal map, after editing one in Photoshop, and after decoding a heavily compressed one. The tools here that understand normal maps already do it for you.
Can it rescue a badly compressed map?
Partly. The washed out look goes away, but the blocky artifacts from the compressor are still baked into the directions.
Related: Combine Normals · Normal Strength · Flip Green