Counts update as you type. Nothing is sent anywhere, which matters more than it sounds when the text is a contract or something unpublished.
This page loads no libraries at all — the work is done by the browser itself. Your file is read on your own machine and never sent anywhere — open your browser's network tab and watch while you use it.
At 200 words a minute, the usual figure for adult reading on screen.
No. Close the tab and it is gone — there is nothing on any server to delete.
Everything here is free and works the same way — in your browser.