Folia Tools
Are online PDF tools safe? What actually happens to your file in the browser
Most online PDF tools upload your document to a server, process it there, and delete it later — on their word. Browser-based tools do not, and the difference is checkable.
The upload model, and what you are agreeing to
The conventional online PDF tool is a web front end for a server. You choose a file, it is uploaded over HTTPS, a program on that server does the work, and you download the result. The file sits on somebody else's disk for as long as their retention policy says, and every promise about what happens to it in the meantime is a promise you cannot verify.
For a holiday itinerary that is completely fine. For an employment contract, an unpublished set of accounts, a medical letter or a client's document that you are under a professional duty to protect, it is a decision that deserves to be made deliberately rather than by default — and it frequently is not, because nothing about the interface signals that a transfer is happening at all.
It is also worth noticing what "we delete your files after an hour" does and does not cover. It says nothing about backups, about logs, about what the processing pipeline retained, or about jurisdiction.
What a browser can actually do on its own
The browser you are reading this in is a capable computing platform. It can read a file you select from disk into memory, run compiled code over it at close to native speed through WebAssembly, and hand you the result as a download — all without a single network request carrying your data.
That is how every tool on this site works apart from two. When you drop a file onto Merge PDF or Compress PDF, your browser reads it from your disk into its own memory, the PDF engine runs there, and the result is handed back as a download. Nothing is transmitted. The site is a set of static files; once the page has loaded, it does not need the network again.
The two exceptions are the ones that could not work this way: AI summarise and Translate PDF send text to a cloud model, because the model is the product and it does not fit in a browser. Both say so before you start.
How to verify it rather than believe it
This is the part that matters, because a claim about privacy is worth exactly as much as your ability to check it — and here you can, in about twenty seconds, with tools already in your browser.
Open your browser's developer tools with F12 and select the Network tab. Load a tool page and let it finish. Now clear the request list, drop your file in, and run the operation. Watch what appears. Code and fonts may load; your document will not be in any of it. There is no request carrying your file, because there is nowhere for it to go.
The stronger version of the same test: run the operation with your network disconnected entirely. Load the tool page, turn off wi-fi, then drop the file in. It works. A tool that needed to upload your document could not possibly do that.
This is also why the site can be honest about the two AI tools. If everything ran locally except two features, and those two were quietly sending data anyway, the Network tab would show it to anyone who looked.
The real limit is your own memory
Local processing has a genuine constraint, and it is worth stating plainly rather than discovering it at the wrong moment: everything happens in your device's memory. A server with 64 GB can hold a 2 GB PDF comfortably. Your browser tab cannot.
There is no fixed number, because the ceiling depends on your machine, your browser, how much else is open, and the operation — rasterising every page of a document needs far more headroom than copying pages between files. In practice, ordinary documents are never a problem; very large scans on a modest laptop can be.
The symptoms are worth recognising. A tab that becomes unresponsive, thumbnails that never appear, or an operation that simply stops partway are all memory pressure, not a bug in the file. Closing other tabs genuinely helps, and so does splitting the job — Split PDF into parts, process each, and merge the results. Where the work is routinely that large, the desktop version is not held to a browser tab's memory ceiling, which is the main practical reason it exists.
What this does not protect you from
Local processing solves one problem completely and no others, and it is worth being precise about which.
It does not protect the file on your own disk, or the copy you are about to email. It does not make a redaction correct — Redact PDF rebuilds the page so the text is gone, but choosing which text is still your job, and the guide on why black boxes do not redact exists because that is where people get hurt. It does not encrypt anything; Protect PDF is a separate, deliberate step.
And it says nothing about the rest of the internet. The value of a tool that never receives your document is bounded and specific: whatever else goes wrong, it will not be a leak from a service you used for four seconds and never thought about again.
Questions
Is it safe to use online PDF tools?
It depends entirely on where the work happens, and that is not something you can tell by looking. A site that processes your file on its own servers has your document, whatever its policy says; a site that processes it in your browser never receives it at all, and cannot. The test is the one in this article: open your browser network panel before you convert, and watch whether the file is uploaded. It is a check you can run on any tool site, including this one.
How do I know my file is not being uploaded?
Check it. Open developer tools with F12, select the Network tab, and run an operation — no request carries your document. Or load the page, disconnect from the network, and use the tool anyway. It works, which it could not if it needed a server.
Which tools do send data somewhere?
Two: AI summarise and Translate PDF. Both need a cloud model that cannot run in a browser, and both tell you before you start. Every other tool on the site runs entirely on your machine.
Is there a file size limit?
None is imposed. The ceiling is your own device's memory, which differs from one computer to another. Very large scans on a modest laptop can run out of headroom; ordinary documents never do.
Why did the page freeze on a big document?
Almost always memory pressure rather than a defect. Close other tabs and try again, or split the document, process the parts and merge the results. For work that is routinely that large, the desktop version is not held to a browser tab's memory ceiling.
Do I need an account?
No. There is no sign-up, no upload, no watermark and no per-day limit, because your own computer does the work and that costs nothing to provide.