Massive market data API is the renamed Polygon.io

massive.com / api.massive.com is Polygon.io after a rebrand, so every Polygon endpoint path still applies verbatim: /v2/snapshot/locale/us/markets/stocks/{tickers,gainers,losers}, /v2/aggs/ticker/{t}/range/{mult}/{span}/{from}/{to}, /v2/reference/news, /v3/reference/tickers. Auth accepts either an apiKey query param or Authorization: Bearer, and the env var their docs assume is MASSIVE_API_KEY. Do not confuse it with joinmassive.com (a bandwidth/proxy product) — different company. Gotcha carried over from Polygon: the snapshot day bar is all zeros before the session opens, so coerce 0 to null and fall back to prevDay.c or the UI shows $0.00 pre-market; movers and news also require the Stocks Starter plan or above and 403 on free tiers.