I'm designing a web app where you can download a single file or a dynamically-generated zip file of several files.
For single files, I am planning for the file to be downloaded immediately.
For multiple files, there may be a long delay before the zip file is generated so I am providing a busy indicator. After the zip is ready, the download is automatically triggered.
I am considering providing a message here that says "Your download will start shortly. If it does not start automatically, click here."
Is this necessary?
I know apps like Dropbox don't offer this, but they might be catering for more savvy users who know that they need to disable download blockers etc.