These two terms get used interchangeably, but they describe different types of grooming tools with different designs and different origins.
A shedding blade is a traditional horse grooming tool. It’s typically a long, looped or straight metal blade with a serrated or toothed edge, used in long strokes across a horse’s coat to scrape away loose hair and surface debris. The term comes from the equestrian world and has been in use for decades. Some dog grooming tools have borrowed the name, though the designs vary widely.
A deshedding tool is a broader, more modern category that covers any tool specifically engineered to remove dead undercoat. The category includes several different designs and mechanisms, and the term is more commonly used in pet grooming than in traditional horse care.
The overlap in terminology is mostly a marketing problem. Different brands use both terms loosely, which makes comparison shopping harder than it needs to be. When evaluating any tool, the mechanism matters more than what it’s called.

