Initiate Download

A few practical options beyond the basic link that @Comatose suggested, with notes that address the server and browser quirks mentioned by @MidiMagic and the HTML style tip from @macneato.

The easiest modern client-side method is the HTML5 download attribute on an anchor. It lets the browser suggest a download instead of trying to open the file. Example:

<a href="/files/myfile.zip" download>Download ZIP</a>
<a href="/files/myfile.zip" download="project-archive.zip">Save as project-archive.zip</a>

This is subject to same-origin/CORS rules and browser behavior — see MDN: a[download] attribute.

For full control (and to force-download file types like PDFs or images), have the server send a Content-Disposition header. A common PHP pattern:

<?php
$file = '/path/to/file.zip';
if (is_readable($file)) {
  header('Content-Type: application/octet-stream');
  header('Content-Disposition: attachment; filename="file.zip"');
  header('Content-Length: ' . filesize($file));
  readfile($file);
  exit;
}
?>

Validate paths (no user-controlled paths), check permissions, and stream large files in chunks or use server-level sendfile/X-Accel/X-Sendfile to avoid memory issues. Relevant spec: MDN: Content-Disposition header.

If you want a button instead of a visible link, create an anchor dynamically and trigger a click in JS (better than auto-redirecting on page load which is jarring and blocked by some browsers). Also remember: hosting providers can block direct serving of some extensions, and browser PDF viewers may still preview instead of downloading unless Content-Disposition: attachment is used.