Indexing is the state in which Amazon's search engine has recorded that your listing is relevant to a particular word or phrase, so the listing is eligible to appear when a shopper searches for it. Indexing is binary and comes before rank: a listing that is not indexed for "insulated lunch bag" cannot appear on any page for that search, no matter how much you bid, while a listing that is indexed can appear anywhere from position 1 to position 300.
Why it matters
Most "my keyword is not working" problems are indexing problems. A term can drop out of the index when a title is edited, when the backend field goes over its byte limit, when a category or browse node changes, or when Amazon's relevance model decides the word no longer fits the product. When that happens, both organic traffic and Sponsored Products impressions for the term stop, because ads also require the listing to be relevant to the query.
Indexing also has a quality dimension. Amazon indexes a listing for words in the title, bullets, structured attributes and backend field, but it weighs them differently, and it can index a listing for a term without ranking it anywhere useful. Being indexed is necessary, not sufficient.
What moves it
- Where the word appears. The title carries the most weight, then bullets and attributes, then the backend field.
- Field limits. Titles over the category's character limit and backend fields over 250 bytes can be ignored wholesale.
- Relevance signals. Sales and clicks from a search reinforce indexing for that term; none over a long period can weaken it.
- Prohibited words. Terms that violate Amazon's policy can be stripped from the index.
- Variation structure. Child ASINs can index for words in the parent's content, and vice versa, depending on the category.
How we use it
Every keyword on a listing's map is verified as indexed 48 hours after upload, by searching the term together with the ASIN and by watching for impressions in Search Query Performance. Terms that fail are traced to the field they sit in and fixed there. We repeat the check monthly and after any content edit, because indexing losses are silent until the traffic report shows them.