 <p>The parameters to <code>glfwOpenWindow</code> are specifying the desired values. However, it's entirely possible that your driver doesn't support the exact format you're asking for (24 bit color, 24 bit depth, no alpha, no stencil). GLFW will attempt to find the best match while meeting your minimums.</p> <p>In this case it's probably giving you the most standard format of RGBA color (32 bit) and a 24/8 bit depth/stencil buffer, or it could be creating a 32 bit depth buffer. You'd actually need to call <code>glfwGetWindowParam</code> to query the depth and stencil bits for the default framebuffer, and then build your renderbuffers to match that. </p>