Plain guide
You made something. A design, a manuscript, a photo, a contract draft, a piece of code. You are worried someone else will claim it first, or you need to show that a file existed, unchanged, on a particular day. Here is the honest answer, written to be useful whether or not you ever use our tool.
If this is happening right now, do three things before you read the rest. Stop editing the file, and work on a copy instead, because every edit changes the fingerprint. Keep the messy working files, the drafts, the notes, the earlier versions, because those speak to who made it in a way a fingerprint cannot. Then put a dated record somewhere outside your own control, using any option below. Ten minutes of that is worth more than a perfect plan you make next week.
You can prove this: that a file existed in exactly this form no later than a certain date. That is it. And you can only prove it if a fingerprint of the file was placed somewhere dated that you do not control, at the time.
Nobody can prove these: that you were the first person to think of it, that you wrote it rather than copied it, that you own it, or that the file is older than the record. Any tool promising those is promising something no tool does.
Two things people try first, and why they are weak:
The thing that makes a date mean something is simple: the record has to be somewhere you could not have gone back and changed. That is the whole idea, and everything below is a different way of buying it.
A fingerprint, usually called a SHA-256 hash, is a short string of 64 characters computed from the exact bytes of a file. It looks like this:
e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
Three things are worth knowing about it, and one honest catch.
So the useful move is: publish the fingerprint somewhere dated, keep the file. Later, to prove the file existed then, you hand over the file, anyone recomputes its fingerprint, and it matches the dated record. The file stayed private the whole time.
These are the real choices. Most of them are not us, and the first one costs nothing.
The unglamorous one that carries more weight than people expect. Drafts, sketches, version history, the messy file with the layers still in it, notes and messages where you discussed it while you were making it. A trail of work in progress is hard to fake after the fact and speaks to authorship, which a fingerprint cannot.
Cost: free, plus the discipline to keep things. Weakness: all of it sits in your own control, so someone who thinks you are lying can say you made it later. Use it alongside a dated outside record, not instead of one.
A person with a professional duty records that they saw a document on a date, and their register is kept outside your control. Old, well understood, and respected in places where an unfamiliar technical record is not.
Cost: a fee per document and a trip, often more for large or unusual files. Weakness: it does not scale to a hundred files, it usually means handing over the contents, and what it does and does not establish depends entirely on where you are.
Many countries run a registry for creative works. Where it applies to what you made, it is the strongest option on this page, because it is built to answer the ownership question rather than just the date question.
Cost: a fee and a wait, sometimes months. Weakness: it is specific to your jurisdiction and to the kind of work, and it does not cover everything. We are not lawyers and nothing on this page is legal advice. If real money, a deadline or a dispute is involved, talk to one before you rely on any of this.
Post the 64 characters in a place that carries its own timestamp and is not yours to rewrite. A public post, a comment thread, a mailing list archive, a printed classified ad. You can do this today for free, with no tool at all.
Cost: usually free. Weakness: the platform can delete it, change its own timestamps, or close. Explaining a string of 64 characters in an old social post to a skeptical stranger is its own project. Posting in several places at once is a cheap way to make it sturdier.
A service takes your fingerprint and records it in a dated log it publishes. Some are free, some charge, some write into public infrastructure that is genuinely hard for any one party to rewrite. Fast, repeatable, and it never sees your file.
Cost: free to small. Weakness: you are trusting whoever keeps the record, and the honest question to ask any of them, including us, is what happens to your evidence if that operator disappears. If the answer is vague, keep your own copy of the record.
A dated record of a fingerprint proves a date. It does not prove any of the following, and no amount of stamping will change that.
Being first to record something is still useful, because in most arguments about who had a thing first, nobody has anything dated at all. Just know precisely which question you have answered.
We run arcaeon.io/stamp. It is free, three stamps a day. You pick a file, your browser computes the fingerprint on your own machine, and only the fingerprint and the file size are sent. The file never leaves your computer. The first stamp of a fingerprint wins, so stamping the same file again returns the original record and its original time. Each stamp gets a permanent link at arcaeon.io/r/ followed by the fingerprint, which you can save or send to anyone. Checking whether a file is already stamped is free and does not use up a stamp.
The limit, stated in the same breath, because you should weigh it before relying on this: the record is one public repository, written by one operator and hosted by one code host. That is an outside party, but it is not an independent one. If that repository is deleted, or its history is rewritten, the record goes with it. It is public, so anyone can copy or mirror it, and a copy you hold yourself is the strongest form of this. Save your permanent link, and save the fingerprint next to your file.
The full version of what each of our tools does and does not establish is on what Arcaeon proves, and what it does not. If you were handed a receipt from one of our tools, you can check it yourself at verify a receipt, free and in your own browser.
None of this needs us, and you can finish the list in about twenty minutes.