What Is the Williams Alligator Indicator?

Legendary trader Bill Williams, an early pioneer of market psychology, developed the trend-following Alligator indicator, which follows the premise that financial markets and individual securities trend just 15% to 30% of the time while grinding through sideways ranges the other 70% to 85% of the time. Williams believed that individuals and institutions tend to collect most of their profits during strongly trending periods.

Key Takeaways

  • The Williams Alligator indicator is a technical analysis tool that uses smoothed moving averages.
  • The indicator uses a smoothed average calculated with a simple moving average (SMA) to start.
  • It uses three moving averages, set at five, eight, and 13 periods. The three moving averages comprise the Jaw, Teeth, and Lips of the Alligator.
  • The indicator applies convergence-divergence relationships to build trading signals, with the Jaw making the slowest turns and the Lips making the fastest turns.

How the Williams Alligator Indicator Works

The Alligator indicator uses three smoothed moving averages, set at five, eight, and 13 periods, which are all Fibonacci numbers. The initial smoothed average is calculated with a simple moving average (SMA), adding additional smoothed averages that slow down indicator turns.

Calculation of the Alligator Indicator

Simple moving average (SMA):



Subsequent values are:




SUM1 - the sum of closing prices for N periods;

PREVSUM - smoothed sum of the previous bar;

SMMA1 - smoothed moving average of the first bar;

SMMA(i) - smoothed moving average of the current bar (except for the first one);

CLOSE(i) - current closing price;

N - the smoothing period.

How the indicator is calculated is important for understanding the inner workings of the indicator. Luckily, the calculation is not required in practice. The Alligator indicator can be added to your charts from the indicator list in your charting or trading platform.

The three moving averages comprise the Jaw, Teeth, and Lips of the Alligator, opening, and closing in reaction to evolving trends and trading ranges:

  1. Jaw (blue line): Starts with the 13-bar SMMA and is smoothed by eight bars on subsequent values.
  2. Teeth (red line): Starts with the eight-bar SMMA and is smoothed by five bars on subsequent values.
  3. Lips (green line): Starts with the five-bar SMMA and smoothed by three bars on subsequent values.

Williams invoked barnyard imagery to describe the indicator, noting "even a blind chicken will find its corn if it is always fed at the same time ... it took us years but we have produced an indicator that lets us always keep our powder dry until we reach the blind chicken's market." 

Special Considerations

The indicator applies convergence-divergence relationships to build trading signals, with the Jaw making the slowest turns and the Lips making the fastest turns. The Lips crossing down through the other lines signals a short sale opportunity while crossing upward signals a buying opportunity. Williams refers to the downward cross as the alligator "sleeping" and the upward cross as the alligator "awakening." 

The three lines stretched apart and moving higher or lower denote trending periods in which long or short positions should be maintained and managed. This is referred to as the alligator "eating with mouth wide open." Indicator lines converging into narrow bands and shifting toward a horizontal direction denote periods in which the trend may be coming to an end, signaling the need for profit-taking and position realignment. This indicates the alligator is "sated."

The indicator will flash false positives when the three lines are crisscrossing each other repeatedly, due to choppy market conditions. According to Williams, the alligator is "sleeping" at this time. Remain on the sidelines until it wakes up again. This exposes a significant drawback of the indicator because many awakening signals within large ranges will fail, triggering whipsaws.

Example of the Williams Alligator Indicator

Image by Sabrina Jiang © Investopedia 2020

Facebook, Inc. (FB) has an alligator "awakening" signal near the bottom left of the chart, then embarks on a strong uptrend that shows an alligator "eating with open mouth" phase. On the rise, the price drops to the Jawline, but the indicators do not cross each other. The trend remains up. An alligator "sated" sell signal arrives when the Lips cross below the Teeth and Jawlines and lines intertwine as the price moves sideways.

The alligator "sleeps" for some time before a new awakening signal goes off, and uptrend commences with another "eating with an open mouth" phase. The price continues to rise but in a weak fashion. Then there is a sell-off and the mouth opens to the downside, signaling a downtrend. The lines cross again, signaling that the alligator is "sated." Until the mouth opens again, remain on the sidelines.

The Alligator indicator can be used in any market or time frame. Next is an example of the EUR/USD currency pair.

Image by Sabrina Jiang © Investopedia 2020 

In the lower-left of the chart, the Alligator opens up, and an uptrend remains in place for some time. The lines then cross, and two small downtrends develop. This is followed by a buy signal to the upside, which results in a brief uptrend. As the price pulls back, the Alligator is sated, and then it opens again for a big uptrend. This is followed by an extended sideways period, in which the indicator lines crisscross back and forth. This is a sleeping phase, and most traders are best to stay away. At the far right of the chart, the Alligator is opening its mouth again, or awakening, signaling a downtrend.

Bill Williams' Alligator indicator provides a useful visual tool for trend recognition and trade entry timing, but it has limited usefulness during choppy and trendless periods. Market players can confirm buy or sell signals with a moving average convergence divergence (MACD) or another trend identification indicator.