What annoys you most about online file converters?

I launched a file tools site today, and while building it I kept a list of things that drove me mad on other converters: sign-up walls after the first file, watermarks on the output, tiny size limits, and pages so full of ads you can’t find the download button.

I’m curious what’s on your list. Is it privacy (where do my files go?), speed, file size limits, or something else entirely?

For context, mine is TypeorDrop. Files are deleted automatically, and you can start without signing up. I’d rather hear what’s still wrong than what’s fine, so be honest.