I found this with Google:
http://stackoverflow.com/questions/3717793/javascript-file-upload-size-validation
You can do it with GWT I suppose.
2013/7/5 Kedar Vyawahare
> Hi,
> I want to make validation not to upload a file more than 100 MB in my file
> up loader widget.
> Currently I am uploading the file and transfering it on server side and
> there on server side checking the size.
> Is there any way so that I can check the file size on client side itself
> so that it will reduce the time
> required for file transfer to server side.
>
> --
>
> Thanks & regards ,
>
> Kedar
>
>
>
> --
> You received this message because you are subscribed to the Google Groups
> "Google Web Toolkit" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to google-web-toolkit+unsubscr...@googlegroups.com.
> To post to this group, send email to google-web-toolkit@googlegroups.com.
> Visit this group at http://groups.google.com/group/google-web-toolkit.
> For more options, visit https://groups.google.com/groups/opt_out.
>
>
>
--
You received this message because you are subscribed to the Google Groups
"Google Web Toolkit" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to google-web-toolkit+unsubscr...@googlegroups.com.
To post to this group, send email to google-web-toolkit@googlegroups.com.
Visit this group at http://groups.google.com/group/google-web-toolkit.
For more options, visit https://groups.google.com/groups/opt_out.
