What is the correct way to release memory allocated in Emscripten/WebAssembly?

I created web assembly (C++) by Emscripten. I am making some tests in JS to clarify how memory allocation works.
I have click button handler

function handler() {
    const imageData = getCanvasImage();
    const buffer = imageData.data.buffer;
    const bufSize = imageData.width * imageData.height * 4;

    const dataPtr = Module._malloc(bufSize);
    const dataOnHeap = new Uint8Array(Module.HEAPU8.buffer, dataPtr, bufSize);
    dataOnHeap.set(new Uint8Array(buffer))

    Module._free(dataPtr);
}

I just allocate memory by _malloc and release memory by _free.
Image from my canvas takes 1.4MB.
Every time I click memory of browser grows. (I monitor browser process via ProcessExplorer)

What I do wrong?
How to release memory correctly?

Thanks