How to set name of file downloaded from browser?

Can't find a way in HTML. I think you'll need a server-side script which will output a content-disposition header. In php this is done like this:

header('Content-Disposition: attachment; filename="downloaded.pdf"');

if you wish to provide a default filename, but not automatic download, this seems to work.

header('Content-Disposition: inline; filename="filetodownload.jpg"');

In fact, it is the server that is directly serving your files, so you have no way to interact with it from HTML, as HTML is not involved at all.

When they click a button to download the file, you can add the HTML5 attribute download where you can set the default filename.

That's what I did, when I created a xlsx file and the browser want to save it as zip file.

<a href="path/to/file" download="renamed.txt">Download</a>
<a href="downloads/export.xlsx" download="Data-Export.xlsx">Download Export</a>