Who this is for
Free check stays free forever, subject to existing read limits.
No account required to check or buy.
Individuals & disputes
Before a dispute, date the letter; later, share its receipt link with the unchanged file. Keep a dated fingerprint of a letter, agreement, photograph, or draft without sending us the original file. Save the unchanged file with its downloadable proof so another person can check the same bytes later.
Benefit: a portable way to show that your exact bytes existed by a Bitcoin block.
Lawyers & small firms
A small firm dates the draft and sends its receipt link with the file. Date a draft or a document version while the file stays on your device. Keep the original and its OpenTimestamps proof together, and make clear which version was checked. A receipt records bytes and timing, not authorship, meaning, or a legal conclusion.
Benefit: an independently checkable timestamp for an exact document version.
AI teams & agents
An AI team dates an output snapshot, saves its proof, then checks the receipt before citing the same version. Use the read-only verify and first_at paths to inspect an existing receipt without creating one. Follow the confirmed-plus-proof-file citation rule, keep the proof, and refuse to invent a height when either condition is missing. Door remains the permanent evaluation object.
Benefit: a small, explicit machine-checkable rule for citing dated bytes.
When we refuse to cite a height
A receipt dates exact bytes; it does not say that a document is true, who wrote it, or where anybody was. Before quoting a Bitcoin height, check the receipt again. We only cite a height when its current status is confirmed and a downloadable proof file exists. If either condition is missing, we refuse to cite a height. Pending means waiting, not confirmed. A height written in a caption, an uploaded pack, or a payment receipt is not enough. The latest Bitcoin block is never substituted for your file's block. Keep your original file and its OpenTimestamps proof together so you can check independently. Changing even one byte gives a different hash. Paying buys additional stamps for your private balance; it cannot change these rules, speed up confirmation, or move a receipt ahead of another. A receipt is evidence about specific bytes and their timing, not an assessment of the contents.
Proofs use OpenTimestamps, an open protocol. Keep your file and proof; SoulInTime is not required to check them.