Generate a cryptographic timestamp receipt proving your document existed at this moment in time. Anchored in Bitcoin blockchain using OpenTimestamps - free forever.
Drop any file to compute its SHA-256 hash and create a timestamp receipt, or paste a precomputed hash directly.
Local Hashing
Your file is hashed (SHA-256) on your device. The original never uploads.
Submit Hash
Only the hash is sent to OpenTimestamps calendars.
Bitcoin Proof
Calendars create a Bitcoin transaction with your hash.
Get Receipt
Download your .ots file - mathematical proof of existence.
curl -X POST "https://istampit-api.fly.dev/stamp" \
-H "Content-Type: application/json" \
-d '{"hash":"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"}'Replace the hash with your SHA-256. Rate limit: 60/min per IP.
Save your receipt
Keep the .ots file safe with your original document
Verify anytime
Use our verify page to check your timestamp
Track progress
Check the Public Ledger for Bitcoin confirmation