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---
title: "WebGLRenderingContext: blendEquation() method"
short-title: blendEquation()
slug: Web/API/WebGLRenderingContext/blendEquation
page-type: web-api-instance-method
browser-compat: api.WebGLRenderingContext.blendEquation
---
{{APIRef("WebGL")}}
The **`WebGLRenderingContext.blendEquation()`** method of the
[WebGL API](/en-US/docs/Web/API/WebGL_API) is used to set both the RGB blend
equation and alpha blend equation to a single equation.
The blend equation determines how a new pixel is combined with a pixel already in the
{{domxref("WebGLFramebuffer")}}.
## Syntax
```js-nolint
blendEquation(mode)
```
### Parameters
- `mode`
- : A {{domxref("WebGL_API/Types", "GLenum")}} specifying how source and destination colors are combined.
Must be either:
- `gl.FUNC_ADD`: source + destination (default value)
- `gl.FUNC_SUBTRACT`: source - destination
- `gl.FUNC_REVERSE_SUBTRACT`: destination - source
When using the {{domxref("EXT_blend_minmax")}} extension:
- `ext.MIN_EXT`: Minimum of source and destination
- `ext.MAX_EXT`: Maximum of source and destination
When using a {{domxref("WebGL2RenderingContext", "WebGL 2 context", "", 1)}},
the following values are available additionally:
- `gl.MIN`: Minimum of source and destination
- `gl.MAX`: Maximum of source and destination
### Exceptions
If _mode_ is not one of the three possible values, a
`gl.INVALID_ENUM` error is thrown.
### Return value
None ({{jsxref("undefined")}}).
## Examples
To set the blend equation, use:
```js
gl.blendEquation(gl.FUNC_ADD);
gl.blendEquation(gl.FUNC_SUBTRACT);
gl.blendEquation(gl.FUNC_REVERSE_SUBTRACT);
```
To get the blend equations, query the `BLEND_EQUATION`,
`BLEND_EQUATION_RGB` and `BLEND_EQUATION_ALPHA` constants which
return `gl.FUNC_ADD`, `gl.FUNC_SUBTRACT`,
`gl.FUNC_REVERSE_SUBTRACT`, or if the {{domxref("EXT_blend_minmax")}} is
enabled: `ext.MIN_EXT` or `ext.MAX_EXT`.
```js
gl.getParameter(gl.BLEND_EQUATION_RGB) === gl.FUNC_ADD;
// true
gl.getParameter(gl.BLEND_EQUATION_ALPHA) === gl.FUNC_ADD;
// true
```
## Specifications
{{Specifications}}
## Browser compatibility
{{Compat}}
## See also
- {{domxref("WebGLRenderingContext.blendColor()")}}
- {{domxref("WebGLRenderingContext.blendFunc()")}}
- {{domxref("EXT_blend_minmax")}}