Cross-browser checking on file size at client side before uploading it to the server?

Question

Client side validation is important to improve usability.

Is there any cross-browser way to validate the file size before uploading it to the server. I am using asp.net file upload control.

I found some third-party controls do that check:

http://ajaxuploader.com/Demo/simple-upload.aspx

and

http://demo.essentialobjects.com/Default.aspx?path=AJAXU

but How?

Answer 1

Not possible I am afraid unless you use a flash uploader like swfupload.

Answer 2

The only way to 'know' the filesize before it is sent over to the server is to have a 'thicker than javascript' client-side plugins/add-ons. These will have to be installed on the client system. E.g. using SWFUpload, Java applets, ActiveX controls.

Answer 3

Why? A decent webserver will return a 410 the moment it got a content length header larger than expected.