Guide
How to prove you predicted something before it happened
You called it, and now nobody believes you. The fix is to lock in a prediction before the event, in a way nobody can quietly edit afterward, not even you.
Why a screenshot or a tweet isn’t proof
- Screenshots can be faked in seconds, and the date on them is whatever the screenshot says.
- Social posts can be deleted, and some platforms let you edit them. Anyone suspicious has to trust the platform’s timestamp.
- Cherry-picking is the bigger problem. Someone who makes 20 guesses and shows only the 3 that hit looks like a genius. Proof of one prediction says nothing about the misses.
What actually works: a fingerprint with an independent timestamp
The trick is a commitment. You run your prediction through a hash function like SHA-256, which turns any text into a 64-character fingerprint. Change one comma and the fingerprint changes completely. You publish the fingerprint now and keep the text secret. Later you reveal the text, and anyone can recompute the fingerprint to check that it matches.
That proves the text didn’t change. To prove when you published the fingerprint, you need a timestamp nobody controls. OpenTimestamps provides one by recording fingerprints in the Bitcoin blockchain. It’s free and can’t be backdated.
One more detail: short predictions like “Dodgers” could be guessed by hashing every team name. Adding a long random secret (a nonce) to the text before hashing makes guessing impossible.
The easy way: seal it on Sealed Posts
- Write your prediction on the home page. Add a public headline if you want people to know what it’s about, like “Who wins the World Series.”
- Choose Sealed until… and pick a reveal date after the event.
- Hit Seal it. You get a link right away showing the headline, a countdown, and the fingerprint. The text and its nonce stay hidden.
- Share the link. When the date arrives, the post opens on its own, with a check showing the text matches the original fingerprint.
Every post is sent to OpenTimestamps automatically, and you can download the .ots proof file to verify it with any OpenTimestamps tool, without trusting us.
Beating the cherry-picking problem
Post under an account, and keep your predictions listed. Your profile then shows every listed prediction, hits and misses alike, and nothing can be deleted. A private post can never be switched to listed later, and your profile shows how many private posts you have. That combination is what makes a track record believable.
Doing it by hand
If you’d rather not use any website, you can do the same thing yourself. Write your prediction plus a long random string to a text file, then run sha256sum prediction.txt and post the fingerprint publicly. Stamp the file with the OpenTimestamps client (ots stamp prediction.txt) and keep both files safe. To reveal it, publish the file and the .ots proof. It works, but you have to keep the files, and other people need to know how to check them.