People "call it in advance" on Bluesky by posting a hash, then later posting the string that supposedly produces it — a commitment scheme so nobody can accuse them of changing their answer after the fact. The trick only works if someone actually checks. Paste the hash and the claimed source below; this recomputes it entirely in your browser — nothing is sent anywhere — and tells you whether the claim holds up.
A hash function turns any text into a fixed-length fingerprint —
the same input always produces the same output, but you can't work
backwards from the output to guess the input. That's what makes it
useful as a commitment: post hash(answer) today,
reveal answer tomorrow, and anyone can independently
recompute hash(answer) and confirm it's the same
string you committed to earlier — no trust required.
The usual failure mode isn't a fake claim, it's an honest mismatch from whitespace: a trailing newline, a leading space from a copy- paste, smart quotes swapped in by an app. hashclaim tries a handful of common variants of your source text automatically (as pasted, trimmed, with a trailing newline, with surrounding quotes stripped) and tells you which one, if any, actually lands.