How do I find the Amazon categories or Search Index Matrix? That was a real devil of a question to solve! I didn’t find any helpful links, only dead ends. On top of it all I had no idea they were called Search Indexes. Lets not also leave out the fact that they vary depending on locations in the world. Here is where I found them: Search Index and ItemSearch Parameter Combinations. You will need to expand the tree “API Reference” –> “Search Index and ItemSearch Parameter Combinations” . Does anyone reading this most not have to retrieve them programmatically?