Web/API/WebGLRenderingContext/getActiveUniform

The WebGLRenderingContext.getActiveUniform() method of the WebGL API returns a WebGLActiveInfo object containing size, type, and name of a uniform attribute. It is generally used when querying unknown uniforms either for debugging or generic library creation.

Syntax

WebGLActiveInfo WebGLRenderingContext.getActiveUniform(program, index);

Parameters

program: A WebGLProgram specifying the WebGL shader program from which to obtain the uniform variable's information.
index: A GLuint specifying the index of the uniform attribute to get. This value is an index 0 to N - 1 as returned by gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS).

Return value

A WebGLActiveInfo object describing the uniform.

The type attribute of the return value will be one of the following:

gl.FLOAT
gl.FLOAT_VEC2
gl.FLOAT_VEC3
gl.FLOAT_VEC4
gl.INT
gl.INT_VEC2
gl.INT_VEC3
gl.INT_VEC4
gl.BOOL
gl.BOOL_VEC2
gl.BOOL_VEC3
gl.BOOL_VEC4
gl.FLOAT_MAT2
gl.FLOAT_MAT3
gl.FLOAT_MAT4
gl.SAMPLER_2D
gl.SAMPLER_CUBE
When using a WebGL 2 context, the following values are possible additionally:
- gl.UNSIGNED_INT
- gl.UNSIGNED_INT_VEC2
- gl.UNSIGNED_INT_VEC3
- gl.UNSIGNED_INT_VEC4
- gl.FLOAT_MAT2x3
- gl.FLOAT_MAT2x4
- gl.FLOAT_MAT3x2
- gl.FLOAT_MAT3x4
- gl.FLOAT_MAT4x2
- gl.FLOAT_MAT4x3
- gl.SAMPLER_3D
- gl.SAMPLER_2D_SHADOW
- gl.SAMPLER_2D_ARRAY
- gl.SAMPLER_2D_ARRAY_SHADOW
- gl.SAMPLER_CUBE_SHADOW
- gl.INT_SAMPLER_2D
- gl.INT_SAMPLER_3D
- gl.INT_SAMPLER_CUBE
- gl.INT_SAMPLER_2D_ARRAY
- gl.UNSIGNED_INT_SAMPLER_2D
- gl.UNSIGNED_INT_SAMPLER_3D
- gl.UNSIGNED_INT_SAMPLER_CUBE
- gl.UNSIGNED_INT_SAMPLER_2D_ARRAY

When gl.linkProgram is called, WebGL creates a list of active uniforms. These are possible values of the name attribute of return values of getActiveUniform. WebGL generates one or more entries in the list depending on the declared type of the uniform in the shader:

Single basic type: one entry with the name of the uniform. E.g. uniform vec4 a; will result in a.
Array of basic type: one entry with the name of the uniform suffixed with [0]. E.g. uniform vec4 b[]; will result in b[0].
Struct type: one entry for each member of the struct. E.g. uniform struct { float foo; vec4 bar; } c; will result in c.foo and c.bar.
Arrays of structs or arrays: each entry of the array will generate its own entries. E.g. uniform struct { float foo; vec4 bar; } d[2]; will result in:
- d[0].foo
- d[0].bar
- d[1].foo
- d[1].bar
Uniform blocks: one entry for each member. If the uniform block has an instance name, the block name is prefixed. E.g. uniform Block { float foo; }; will result in foo, and uniform Block { float bar; } e; will result in Block.bar.

The size attribute of the return value corresponds to the length of the array for uniforms declared as arrays. Otherwise, it is 1 (this includes interface blocks instanced with arrays).

Exceptions

gl.INVALID_VALUE is generated if the program WebGLProgram is invalid (not linked, deleted, etc.).
gl.INVALID_VALUE is generated if index is not in the range [0, gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS) - 1].

Examples

const numUniforms = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
for (let i = 0; i < numUniforms; ++i) {
  const info = gl.getActiveUniform(program, i);
  console.log('name:', info.name, 'type:', info.type, 'size:', info.size);
}

Specifications

Specification	Status	Comment
WebGL 1.0The definition of 'getActiveUniform' in that specification.	Recommendation	Initial definition.
OpenGL ES 2.0The definition of 'glGetActiveUniform' 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
`getActiveUniform`	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