Web/API/WebGLRenderingContext/viewport

The WebGLRenderingContext.viewport() method of the WebGL API sets the viewport, which specifies the affine transformation of x and y from normalized device coordinates to window coordinates.

Syntax

void gl.viewport(x, y, width, height);

Parameters

x: A GLint specifying the horizontal coordinate for the lower left corner of the viewport origin. Default value: 0.
y: A GLint specifying the vertical coordinate for the lower left corner of the viewport origin. Default value: 0.
width: A non-negative Glsizei specifying the width of the viewport. Default value: width of the canvas.
height: A non-negative Glsizei specifying the height of the viewport. Default value: height of the canvas.

Return value

None.

Errors thrown

If either width or height is a negative value, a gl.INVALID_VALUE error is thrown.

Examples

When you first create a WebGL context, the size of the viewport will match the size of the canvas. However, if you resize the canvas, you will need to tell the WebGL context a new viewport setting. In this situation, you can use gl.viewport.

gl.viewport(0, 0, canvas.width, canvas.height);

The viewport width and height are clamped to a range that is implementation dependent. To get this range, you can use the MAX_VIEWPORT_DIMS constant, which returns an Int32Array.

gl.getParameter(gl.MAX_VIEWPORT_DIMS);
// e.g. Int32Array[16384, 16384]

To get the current viewport, query the VIEWPORT constant.

gl.getParameter(gl.VIEWPORT);
// e.g. Int32Array[0, 0, 640, 480]

Specifications

Specification	Status	Comment
WebGL 1.0The definition of 'viewport' in that specification.	Recommendation	Initial definition.
OpenGL ES 2.0The definition of 'glViewport' in that specification.	Standard	Man page of the OpenGL API.

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`viewport`	Chrome Full support 9	Edge Full support 12	Firefox Full support 4	IE Full support 11	Opera Full support 12	Safari Full support 5.1	WebView Android Full support Yes	Chrome Android Full support 25	Firefox Android Full support Yes	Opera Android Full support 12	Safari iOS Full support 8	Samsung Internet Android Full support 1.5

Legend

Full support: Full support