Privacy
The video stays in this browser. Choosing a file does not send it to joestudy.net or to anyone else. The new file is saved by your browser's download.
What the page holds
While the tab is open, the page keeps the file in memory so it can read the duration and encode. Closing the tab drops that copy. There is no account and no file library.
Scripts
This build does not load an analytics script, an ad script, or a font from another site. If a later version adds a cookie-less host metric, this page will name it before that script ships.
The host
When the site is on a host, that host can see the usual connection data for a page view: address, time, and the URL. That is not the video. This build has not been deployed, so there is no live host log to describe beyond that.
Your file
You are responsible for the video you open. Tabceil does not grant you a license to it, and it does not check who owns it.