The Accelerator Oscillator (AC) is a momentum-based indicator developed by Bill Williams, designed to show whether the market’s momentum is accelerating or decelerating. It’s especially useful for identifying potential trend continuations or reversals based on changes in the underlying driving force of price.
This indicator is derived from the Awesome Oscillator (AO), and while the AO provides entry and exit signals, the AC helps you better understand how strong or weak the current momentum is.

How It Works
The AC is calculated by subtracting a 5-period moving average from the Awesome Oscillator.
It’s displayed as a histogram:
Green bars indicate increasing momentum
Red bars indicate decreasing momentum

How to Use It in Your Strategy
Use green bars above the zero line to confirm bullish acceleration
Use red bars below the zero line to spot bearish deceleration
AC is most useful for spotting early signs of reversals or when an existing trend may be losing steam
According to Bill Williams, buying above the zero line or selling below it means you’re trading with momentum, not against it.

Inside FX Replay, you can pair the Accelerator Oscillator with other tools like AO, market structure, or volume shifts to further validate your trade ideas.