How can a Website open a file Browser in a smartphone browser?

I already read many articles and threads but still not able to find the answer I needed.

I am working on a website where the system has the capability of uploading files. It is working on a PC Browser but since it is on the web, using a smartphone is unavoidable for the users so we access the system on a smartphone and discovered that the browse button is not working.

I really need an answer for this, your help will be a big help.