When loading a shader with Raylib, a few properties are set automatically. The list of properties can be found in Raylib’s OpenGL library .

#define RL_DEFAULT_SHADER_ATTRIB_NAME_POSITION     "vertexPosition"    // Bound by default to shader location: RL_DEFAULT_SHADER_ATTRIB_LOCATION_POSITION
#define RL_DEFAULT_SHADER_ATTRIB_NAME_TEXCOORD     "vertexTexCoord"    // Bound by default to shader location: RL_DEFAULT_SHADER_ATTRIB_LOCATION_TEXCOORD
#define RL_DEFAULT_SHADER_ATTRIB_NAME_NORMAL       "vertexNormal"      // Bound by default to shader location: RL_DEFAULT_SHADER_ATTRIB_LOCATION_NORMAL
#define RL_DEFAULT_SHADER_ATTRIB_NAME_COLOR        "vertexColor"       // Bound by default to shader location: RL_DEFAULT_SHADER_ATTRIB_LOCATION_COLOR
#define RL_DEFAULT_SHADER_ATTRIB_NAME_TANGENT      "vertexTangent"     // Bound by default to shader location: RL_DEFAULT_SHADER_ATTRIB_LOCATION_TANGENT
#define RL_DEFAULT_SHADER_ATTRIB_NAME_TEXCOORD2    "vertexTexCoord2"   // Bound by default to shader location: RL_DEFAULT_SHADER_ATTRIB_LOCATION_TEXCOORD2
#define RL_DEFAULT_SHADER_ATTRIB_NAME_BONEIDS      "vertexBoneIds"     // Bound by default to shader location: RL_DEFAULT_SHADER_ATTRIB_LOCATION_BONEIDS
#define RL_DEFAULT_SHADER_ATTRIB_NAME_BONEWEIGHTS  "vertexBoneWeights" // Bound by default to shader location: RL_DEFAULT_SHADER_ATTRIB_LOCATION_BONEWEIGHTS
#define RL_DEFAULT_SHADER_UNIFORM_NAME_MVP         "mvp"               // model-view-projection matrix
#define RL_DEFAULT_SHADER_UNIFORM_NAME_VIEW        "matView"           // view matrix
#define RL_DEFAULT_SHADER_UNIFORM_NAME_PROJECTION  "matProjection"     // projection matrix
#define RL_DEFAULT_SHADER_UNIFORM_NAME_MODEL       "matModel"          // model matrix
#define RL_DEFAULT_SHADER_UNIFORM_NAME_NORMAL      "matNormal"         // normal matrix (transpose(inverse(matModelView)))
#define RL_DEFAULT_SHADER_UNIFORM_NAME_COLOR       "colDiffuse"        // color diffuse (base tint color, multiplied by texture color)
#define RL_DEFAULT_SHADER_UNIFORM_NAME_BONE_MATRICES  "boneMatrices"   // bone matrices
#define RL_DEFAULT_SHADER_SAMPLER2D_NAME_TEXTURE0  "texture0"          // texture0 (texture slot active 0)
#define RL_DEFAULT_SHADER_SAMPLER2D_NAME_TEXTURE1  "texture1"          // texture1 (texture slot active 1)
#define RL_DEFAULT_SHADER_SAMPLER2D_NAME_TEXTURE2  "texture2"          // texture2 (texture slot active 2)