Alain Péteut

Hmm, there should be no size limitation from [FileReader](https://developer.mozilla.org/en-US/docs/Web/API/FileReader). Sorry, I have no explanation for that behaviour yet. Could you please provide a `pip freeze | grep ipywidgets`? For now...

+1 for a standard widget, that would be nice! Binary upload should be easy to support, as there is [FileReader#readAsBinaryString](https://developer.mozilla.org/en-US/docs/Web/API/FileReader/readAsBinaryString).

@jasongrout I just realised that [FileReader#readAsBinaryString](https://developer.mozilla.org/en-US/docs/Web/API/FileReader/readAsBinaryString) is non-standard: *Note that this method is now deprecated as per the 12 July 2012 Working Draft from the W3C.*

There is a non-standard [webkitRelativePath](https://developer.mozilla.org/en-US/docs/Web/API/File/webkitRelativePath) attribute, this could be made available.

See also [migration_guides](https://ipywidgets.readthedocs.io/en/latest/migration_guides.html).

`change['owner'].data` is the decoded data, `change['owner'].filename` is the filename where `change` is the parameter of your handler.

Should we refer to [Notebook extensions](http://jupyter.readthedocs.io/en/latest/migrating.html?highlight=nbextension#notebook-extensions), as in some cases the `--user` flag or `sudo` right are required?

@denfromufa: Agreed, do you know a project where I can learn how to use Travis CI to test the browser side?

`karma` is used in [jupyter-js-services/test/integration_test.py](https://github.com/jupyter/jupyter-js-services/blob/master/test/integration_test.py) See also https://github.com/jupyter/notebook/issues/586

Yes, multi-file support is a somewhat mandatory feature. I'll have a look at it, thanks!