# Bollinger Bands (BBANDS)

> QuantNexus indicator page for Bollinger Bands.

**Route**: `/quantnexus/indicators/bbands/`

## What It Does

Bollinger Bands create a dynamic price envelope around a moving average. They are widely used for breakouts, fades, and volatility expansion detection.

## Formula

`Middle Band = SMA(n)`

`Upper Band = SMA + (k * StdDev)`

`Lower Band = SMA - (k * StdDev)`

## Parameters

- `period` - default `20`
- `devfactor` - default `2`
- `movav` - default `MovingAverageSimple`

## C++23 API

```cpp
#include <nonabt/indicators/bbands.hpp>
auto bbands = std::make_unique<nonabt::BBANDS>(data().close(), 20, 2, "MovingAverageSimple");
```

## Common Usage

- Use BBANDS for mean-reversion setups.
- Use band breaks for trend continuation.
- Use band width for volatility analysis.

## Practical Pattern

Trade a break above the upper band as momentum expansion or a return from the lower band as oversold mean reversion, depending on the broader regime.