diff --git a/spec/index.bs b/spec/index.bs
index fed1f2132f..de2a24584e 100644
--- a/spec/index.bs
+++ b/spec/index.bs
@@ -2391,6 +2391,13 @@ interface GPUCommandEncoder {
         GPUTextureCopyView destination,
         GPUExtent3D copySize);
 
+    void inlineUpdateBuffer(
+        ArrayBuffer source,
+        GPUSize64 sourceOffset,
+        GPUBuffer destination,
+        GPUSize64 destinationOffset,
+        GPUSize64 size);
+
     void pushDebugGroup(DOMString groupLabel);
     void popDebugGroup();
     void insertDebugMarker(DOMString markerLabel);
@@ -2517,6 +2524,52 @@ dictionary GPUImageBitmapCopyView {
     </div>
 </div>
 
+### <dfn method for=GPUCommandEncoder>inlineUpdateBuffer(source, sourceOffset, destination, destinationOffset, size)</dfn> ### {#GPUCommandEncoder-inlineUpdateBuffer}
+
+It's often useful for applications to update buffer data prior to draw or compute operations.
+For example, updating model-view and projection matrices before or interleaved with rendering of a scene.
+When these uploads are small, it's viable to inline the update data into the command buffer.
+This does require more copies than other upload paths, but for small data sizes this overhead is negligible.
+Implementations are expected to warn against using this for medium-to-large buffer updates. (e.g. >64k)
+
+In Vulkan, this is similar to |vkCmdUpdateBuffer|.
+In D3D12, implementations can leverage |ID3D12GraphicsCommandList2::WriteBufferImmediate|.
+Metal might use |makeBuffer(bytesNoCopy:length:options:deallocator:)| around some section of shared command buffer serialization memory.
+
+<div algorithm="GPUCommandEncoder.inlineUpdateBuffer">
+
+  **Arguments:**
+    - {{ArrayBuffer}} |source|
+    - {{GPUSize64}} |sourceOffset|
+    - {{GPUBuffer}} |destination|
+    - {{GPUSize64}} |destinationOffset|
+    - {{GPUSize64}} |size|
+
+  **Returns:** void
+
+  Embed a copy of |source| from |sourceOffset| to |size| into the {{GPUCommandEncoder}}.
+  Encode a command into the {{GPUCommandEncoder}} that copies |size| bytes of data from embedded copy to the |destinationOffset| of another {{GPUBuffer}} |destination|.
+
+  <div class=validusage dfn-for=GPUCommandEncoder.inlineUpdateBuffer>
+        <dfn abstract-op>Valid Usage</dfn>
+
+        Given a {{GPUCommandEncoder}} |encoder| and the arguments {{ArrayBuffer}} |source|, {{GPUSize64}} |sourceOffset|, {{GPUBuffer}} |destination|, {{GPUSize64}} |destinationOffset|, {{GPUSize64}} |size|, the following validation rules apply:
+
+          - |encoder| must be a [=valid=] {{GPUCommandEncoder}}.
+          - |encoder|.{{GPUCommandEncoder/inlineUpdateBuffer()}} must not be called when a {{GPURenderPassEncoder}} is active on |encoder|.
+          - |encoder|.{{GPUCommandEncoder/inlineUpdateBuffer()}} must not be called when a {{GPUComputePassEncoder}} is active on |encoder|.
+          - |destination| must be a [=valid=] {{GPUBuffer}}.
+          - The {{GPUBuffer/[[usage]]}} of |destination| must contain {{GPUBufferUsage/COPY_DST}}.
+          - |size| must be a multiple of 4.
+          - |sourceOffset| must be a multiple of 4.
+          - |destinationOffset| must be a multiple of 4.
+          - (|sourceOffset| + |size|) must not overflow a {{GPUSize64}}.
+          - (|destinationOffset| + |size|) must not overflow a {{GPUSize64}}.
+          - The {{ArrayBuffer/byteLength}} of |source| must be greater than or equal to (|sourceOffset| + |size|).
+          - The {{GPUBuffer/[[size]]}} of |destination| must be greater than or equal to (|destinationOffset| + |size|).
+    </div>
+</div>
+
 ## Programmable Passes ## {#programmable-passes}
 
 <script type=idl>