NDJSON (Newline Delimited JSON) is a streaming-friendly format where each line is a self-contained JSON object. For commerce retrievers, one line = one product with title, canonical URL, description, variants, price, availability, image URLs, and the structured attributes that matter for buyer intent.
Unlike a sitemap (URLs only) or JSON-LD on a page (one product at a time), an NDJSON feed hands the retriever the full catalogue in a single deterministic fetch. Models cite products far more often when they can reason about them in bulk.