Your file never uploads
When you drop a PDF, the page reads it with the browser's local file API and keeps it in memory. Compression uses only that memory copy, and the download is generated from the same copy. No request carries your document anywhere - open the developer tools network tab and you will see the file appear in no request at all.
No accounts, no profiles
There is no sign-up, no login and no user database. The tool cannot associate a file with a person because it never meets either.
This also settles the question of children: the site is not directed to children under 13, and it collects no personal information from anyone, of any age. There is no account to create, no form to fill in and no profile to hold.
No tracking at this stage
The site sets no analytics cookies and loads nothing from a third-party domain. All JavaScript - the PDF engine, the packer for zip downloads - is served from this same domain, and the file you drop never leaves it. One thing does go out: a cookieless page-view ping to Vercel's own analytics, also on this domain. It records the page, the site that referred you and a country inferred at the edge. It never sees your file, and it sets no cookie that follows you to another site.
What remains on your side
Files you download land in your normal downloads folder under your browser's rules. Clearing the tab clears everything the page was holding; there is nothing else to delete on our side, because there is no our side.