Relative Volume (RVOL) API
Which markets are trading on abnormal volume right now — the first scan a day-trader runs to find what is "in play" — computed live from Yahoo Finance daily volume, no key, nothing stored. Price tells you where a market is; volume tells you whether anyone cares. A stock drifting on half its normal volume is noise; the same stock on three times its average is a market reacting to something — earnings, news, a breakout — and that is where the opportunity and the risk live. Relative volume (RVOL) is today's volume divided by its recent average: 1.0 is a normal day, 2.0 is double, and anything above signals unusual participation. For each instrument this API returns today's volume, its 20- and 50-day average volume, the RVOL against each, where today's volume sits as a percentile of the window, the dollar (notional) volume for liquidity, and whether volume is trending up or down. The asset endpoint returns one instrument's full volume profile; the screener endpoint ranks the universe by RVOL, putting the names trading on the most unusual volume — the ones in play — at the top. This is the relative-volume / unusual-activity cut — distinct from the bring-your-own-series volume-indicator tools (OBV, MFI), the crypto volume-by-price profile, the order-flow tape and the price APIs. It is the volume that is out of the ordinary.
api.oanor.com/rvol-api
