What causes "Web backend does not support arrays of buffers" in gfx-rs/wgpu?

Bind each buffer as a separate BindGroupEntry with its own binding index.

Web backend does not support arrays of buffers

Error message

Web backend does not support arrays of buffers

What it means

Raised when creating a bind group whose entry is a BindingResource::BufferArray. Browser WebGPU bind group entries bind one buffer per entry, so an array-of-buffers binding (native-only feature used with non-uniform binding arrays) cannot be expressed and the backend panics.

Source

Thrown at wgpu/src/backend/webgpu.rs:2312

                crate::BindingResource::Buffer(crate::BufferBinding {
                    buffer,
                    offset,
                    size,
                }) => {
                    let buffer = buffer.inner.as_webgpu();
                    let mapped_buffer_binding = webgpu_sys::GpuBufferBinding::new(&buffer.inner);
                    mapped_buffer_binding.set_offset_f64(offset as f64);
                    if let Some(s) = size {
                        mapped_buffer_binding.set_size_f64(s.get() as f64);
                    }

                    webgpu_sys::GpuBindGroupEntry::new_with_gpu_buffer_binding(
                        binding.binding,
                        &mapped_buffer_binding,
                    )
                }
                crate::BindingResource::BufferArray(..) => {
                    panic!("Web backend does not support arrays of buffers")
                }
                crate::BindingResource::Sampler(sampler) => {
                    let sampler = &sampler.inner.as_webgpu().inner;
                    webgpu_sys::GpuBindGroupEntry::new(binding.binding, sampler)
                }
                crate::BindingResource::SamplerArray(..) => {
                    panic!("Web backend does not support arrays of samplers")
                }
                crate::BindingResource::TextureView(texture_view) => {
                    let texture_view = &texture_view.inner.as_webgpu().inner;
                    webgpu_sys::GpuBindGroupEntry::new_with_gpu_texture_view(
                        binding.binding,
                        texture_view,
                    )
                }
                crate::BindingResource::TextureViewArray(..) => {
                    panic!("Web backend does not support BINDING_INDEXING extension")
                }

View on GitHub (pinned to 3e11ff59bf)

Solutions

Bind each buffer as a separate BindGroupEntry with its own binding index.
Pack per-object data into a single larger uniform/storage buffer with dynamic offsets, and use set_bind_group dynamic offsets per draw.
Restrict buffer-array bindings to native backends and provide a web-specific bind group layout.

Example fix

// before
entries.push(wgpu::BindGroupEntry { binding: 0, resource: wgpu::BindingResource::BufferArray(&buffers) });
// after
for (i, buf) in buffers.iter().enumerate() {
    entries.push(wgpu::BindGroupEntry { binding: i as u32, resource: wgpu::BindingResource::Buffer(buf.slice(..)) });
}

Defensive patterns

Strategy: validation

Validate before calling

for e in &entries {
    assert!(!matches!(e.resource, wgpu::BindingResource::BufferArray(_)), "BufferArray unsupported on web backend");
}

Type guard

fn is_web_safe_resource(r: &wgpu::BindingResource) -> bool {
    !matches!(r, wgpu::BindingResource::BufferArray(_) | wgpu::BindingResource::SamplerArray(_) | wgpu::BindingResource::TextureViewArray(_))
}

Prevention

Use one bind group entry per buffer with dynamic offsets instead of buffer arrays.
Pack per-object uniforms into a single buffer with dynamic offset alignment.
Validate bind group entries against the backend before create_bind_group in debug builds.

When it happens

Trigger: Calling device.create_bind_group with a BindGroupEntry whose resource is BindingResource::BufferArray(&[...]) on the web backend, typically for bindings declared as arrays of storage/uniform buffers.

Common situations: Using the bindless-style buffer-array patterns on wasm32-web; shared bind group layout code written for native backends; batching many uniform buffers into one array binding.

Related errors

AI-assisted analysis of gfx-rs/wgpu@3e11ff59bf (2026-09-03). Data as JSON: /api/errors/9badb6657b10a145. Report an issue: GitHub.