Relative Strength Index (RSI) API

The RSI API gives you Wilder's classic momentum oscillator for any crypto, stock or forex symbol — in real time or across history. RSI measures the speed and strength of price moves, oscillating 0–100, with readings above 70 flagging overbought and below 30 oversold conditions. One call. Any timeframe. No TA library to maintain.

Type Momentum oscillator Range 0–100 Endpoint /rsi 20+ exchanges Timeframes 1m → 1w

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Code samples: Node · Python · PHP · cURL →

Request

[GET] https://v2.taapi.io/indicator/rsi
     Authorization: Bearer YOUR_API_KEY

     ?exchange=binance
     &symbol=BTC/USDT
     &timeframe=1h

Response

{
  "value":     [65.73],
  "timestamp": [1718233200]
}

Need every parameter, the full response schema and language SDKs? Full Relative Strength Index (RSI) developer reference →

What is Relative Strength Index (RSI)?

The Relative Strength Index (RSI), developed by J. Welles Wilder Jr. in 1978, is a momentum oscillator that measures the speed and magnitude of recent price changes. It compares the average gain to the average loss over a chosen period (default 14 candles) and normalises the result to a 0–100 scale. RSI is one of the most widely used indicators in technical analysis, trusted by traders in crypto, equities and forex to spot overbought and oversold conditions, divergences, and trend direction.

How to read Relative Strength Index (RSI)

Where the reading sits tells you about momentum and possible exhaustion.

Above 70 · Overbought

70–100

Buying momentum may be overextended. Watch for a stall or reversal signal before entering short.

Around 50 · Trend filter

~50

Above 50 favours bulls, below 50 favours bears. A simple, powerful trend-bias filter.

Below 30 · Oversold

0–30

Selling momentum may be exhausted. Watch for a bounce or reversal before entering long.

Relative trading strategies

Overbought / oversold reversals

Fade extremes: look for shorts as RSI rolls down from above 70, longs as it turns up from below 30. Works best in ranging markets — combine with support/resistance levels.

RSI divergence

Price makes a new high but RSI makes a lower high (bearish divergence) — an early reversal cue. Confirm with buy/sell volume to filter false positives.

The 50-line as a trend filter

Only take long signals while RSI holds above 50, shorts while it stays below. A lightweight way to ensure you trade with the prevailing momentum.

Customising Relative Strength Index (RSI)

The optional 'period' parameter sets how many candles feed the calculation. Shorten to 7–9 for faster, more sensitive signals on intraday charts; lengthen to 21+ to smooth out noise on higher timeframes. The default is 14 — Wilder's original recommendation and still the most widely used setting.

See all parameters in the docs →

Frequently asked questions

What is a good RSI period?

14 is the standard Wilder default and works for most timeframes. Shorten to 7–9 for faster, more sensitive signals on intraday charts (1m–15m); lengthen to 21+ to smooth out noise on daily or weekly charts.

What RSI level is overbought or oversold?

Readings above 70 are conventionally overbought and below 30 oversold. In strong trending markets, some traders widen these to 80/20 to avoid premature counter-trend signals.

How is RSI calculated?

RSI compares the average size of recent gains to recent losses over the chosen period, then normalises the result to a 0–100 scale using the formula: RSI = 100 – (100 / (1 + RS)), where RS = Average Gain / Average Loss. Our API handles the full calculation — you just request the value.

Can I get historical RSI values via the API?

Yes. Use the 'results' parameter to return RSI across the past N candles in one call, or 'backtrack' for a single historical candle. Full detail in the developer docs.

Does RSI work for crypto?

Yes — RSI is one of the most popular indicators in crypto trading. Because crypto markets run 24/7 without session opens/closes, shorter periods (7–9) are often more responsive to the faster volatility.

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Building with the Relative Strength Index (RSI) API?

The developer documentation covers the full technical reference: the /rsi endpoint, every parameter, the response schema, rate limits, bulk queries and ready-to-run samples in Node.js, Python, PHP and cURL.

Open Relative Strength Index (RSI) docs →

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