# Hurst Exponent & Market Regime API > Tells you whether each market is trending, behaving like a random walk, or mean-reverting — the single most important thing to know before choosing a strategy — computed live from Yahoo Finance daily closes, no key, nothing stored. A trend-following system bleeds money in a mean-reverting market, and a fade-the-move system gets run over in a trending one; the Hurst exponent (via rescaled-range R/S analysis) measures which world you are in. A Hurst above ~0.55 means the series is persistent — moves tend to continue, so it trends and trend-following fits; near 0.5 it is a random walk with no edge either way; below ~0.45 it is anti-persistent — moves tend to reverse, so it mean-reverts and fading extremes fits. Alongside it the API returns the Kaufman Efficiency Ratio (net move divided by the total path travelled, 0 = pure noise, 1 = a perfectly straight trend), a second intuitive read on how cleanly a market is trending. The asset endpoint returns one instrument's Hurst, efficiency ratio and a regime label; the screener endpoint ranks the cross-asset universe (equities, sectors, commodities, bonds, FX and crypto; filterable by class) from most trending to most mean-reverting. This is the persistence / trend-versus-mean-reversion regime cut — distinct from the z-score stretch gauges (how far a price is from its average right now, not the structure of its moves), the multi-timeframe momentum-alignment API and the price APIs. It tells you which kind of strategy the market is paying for. ## Authentication All requests require your oanor API key in the `x-oanor-key` header. Get one at https://www.oanor.com/developer/keys. ```bash curl -H "x-oanor-key: oanor_live_…" "https://api.oanor.com/hurst-api/..." ``` ## Pricing - **Free** (Free) — 670 calls/Mo, 2 req/s - **Starter** ($13/Mo) — 14,100 calls/Mo, 6 req/s - **Pro** ($39/Mo) — 79,000 calls/Mo, 16 req/s - **Mega** ($86/Mo) — 458,000 calls/Mo, 40 req/s ## Endpoints ### Screener #### `GET /v1/screener` — Rank the universe from most trending to most mean-reverting **Parameters:** - `metric` (query, optional, string) — hurst or efficiency Example: `hurst` - `window` (query, optional, string) — Lookback in trading days (100-756) Example: `252` - `class` (query, optional, string) — equity, sector, commodity, bond, fx, crypto or all Example: `all` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/hurst-api/v1/screener?metric=hurst&window=252&class=all" ``` **Response:** ```json { "data": { "note": "Ranked by hurst descending (most trending / most efficient first) over window_days of daily closes. Hurst > 0.5 = persistent (trends, trend-following fits); ~0.5 = random walk; < 0.5 = anti-persistent (mean-reverts, fade extremes). Efficiency ratio 0 = pure noise, 1 = a straight trend. Read fresh per call, nothing cached.", "class": "all", "count": 21, "metric": "hurst", "source": "Yahoo Finance", "results": [ { "name": "Gold", "rank": 1, "class": "commodity", "hurst": 0.603, "regime": "strongly trending (persistent — trend-following fits)", "symbol": "GLD", "available": true, "observations": 252, "efficiency_ratio": 0.064 }, { "name": "Bitcoin", "rank": 2, "class": "crypto", "hurst": 0.599, "regime": "strongly trending (persistent — trend-following fits)", "symbol": "BTC-USD", "available": true, "observations": 252, "efficiency_ratio": 0.16 }, { "name": "Utilities", "rank": 3, "class": "sector", "hurst": 0.596, "regime": "strongly trending (persistent — trend-following fits)", …(truncated, see openapi.json for full schema) ``` ### Asset #### `GET /v1/asset` — Hurst, efficiency ratio and regime for one instrument **Parameters:** - `symbol` (query, required, string) — Universe symbol Example: `SPY` - `window` (query, optional, string) — Lookback in trading days (100-756) Example: `252` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/hurst-api/v1/asset?symbol=SPY&window=252" ``` **Response:** ```json { "data": { "name": "S&P 500", "note": "Hurst exponent via rescaled-range (R/S) analysis on log returns over window_days; efficiency ratio = net change / total path travelled on the close series. Hurst > 0.5 trends, < 0.5 mean-reverts. Read fresh per call, nothing cached.", "class": "equity", "hurst": 0.532, "reads": { "hurst": "trending — momentum/trend-following strategies have an edge", "efficiency": "noisy, directionless" }, "regime": "trending (mildly persistent)", "source": "Yahoo Finance", "symbol": "SPY", "window_days": 252, "observations": 252, "efficiency_ratio": 0.138 }, "meta": { "timestamp": "2026-06-12T10:34:47.870Z", "request_id": "bb4595ae-bcbd-4861-9167-719c446c1018" }, "status": "ok", "message": "Asset Hurst retrieved successfully", "success": true } ``` ### Universe #### `GET /v1/universe` — The cross-asset universe and its classes **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/hurst-api/v1/universe" ``` **Response:** ```json { "data": { "note": "The cross-asset universe the screener ranks. Pass class= to a screener call to rank within one class.", "count": 21, "assets": [ { "name": "S&P 500", "class": "equity", "symbol": "SPY" }, { "name": "Nasdaq 100", "class": "equity", "symbol": "QQQ" }, { "name": "US Small Caps", "class": "equity", "symbol": "IWM" }, { "name": "Developed ex-US", "class": "equity", "symbol": "EFA" }, { "name": "Emerging Markets", "class": "equity", "symbol": "EEM" }, { "name": "Technology", "class": "sector", "symbol": "XLK" }, { "name": "Financials", "class": "sector", "symbol": "XLF" }, { "name": "Energy", "class": "sector", "symbol": "XLE" }, { "name": "Health Care", "class": "sector", "symbol": "XLV" }, { "name": "Utilities", "class": "sector", "symbo …(truncated, see openapi.json for full schema) ``` ### Meta #### `GET /v1/meta` — Service metadata **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/hurst-api/v1/meta" ``` **Response:** ```json { "data": { "note": "metric is hurst (default) or efficiency. window is 100-756 trading days (default 252; Hurst needs a long sample). class filters to equity/sector/commodity/bond/fx/crypto (default all). Read fresh per call, nothing cached.", "source": "Yahoo Finance daily closes, live", "classes": [ "equity", "sector", "commodity", "bond", "fx", "crypto" ], "metrics": [ "hurst", "efficiency" ], "service": "hurst-api", "endpoints": { "GET /v1/meta": "This document.", "GET /v1/asset": "Hurst, efficiency ratio and regime for one instrument (symbol=SPY, window=252).", "GET /v1/screener": "Rank the universe by Hurst or efficiency ratio, most trending first (metric=hurst, window=252, class=all).", "GET /v1/universe": "The cross-asset universe and its classes." }, "description": "Hurst exponent & market regime — tells you whether each market is trending, a random walk, or mean-reverting, live from Yahoo Finance daily closes (no key, nothing stored). The Hurst exponent (rescaled-range R/S analysis) above ~0.55 means persistent/trending (trend-following fits), near 0.5 a random walk, below ~0.45 anti-persistent/mean-reverting (fade extremes). The Kaufman efficiency ratio (net move / total path) is a second read on trend cleanliness. asset returns one instr …(truncated, see openapi.json for full schema) ``` --- Marketplace page: https://www.oanor.com/api/hurst-api OpenAPI spec: https://www.oanor.com/api/hurst-api/openapi.json