Proof
without
surrender.
A file fingerprint. A blockchain timestamp. No uploads, no accounts, no backend. OpenProof registers a SHA-256 hash on Base Sepolia. The file never leaves your browser.
Who uses OpenProof
Anyone who needs to prove a file existed at a specific time — without revealing or uploading the file itself.
Developers
Timestamp release artifacts, build outputs, and dependency manifests to verify integrity later.
Creators & artists
Prove your original work existed before publishing, sharing, or sending it to a collaborator.
Researchers & academics
Establish priority of findings, datasets, and preprints before peer review or publication.
Legal professionals
Create independently verifiable timestamps for contracts, disclosures, and records of counsel.
Journalists
Anchoring source material, internal communications, and unpublished drafts to a permanent timestamp.
Businesses & compliance
Document integrity checks for regulatory records, audit trails, and internal policy adherence.
Archivists & preservationists
Long-term integrity verification for digital collections, cultural records, and historical documents.
Individuals
Personal records — wills, letters, receipts, photos, certificates — anyone can timestamp anything.
How it works
Choose a file
Select any file from your device. It is read locally and never uploaded.
Register the hash
OpenProof hashes the file with SHA-256 in your browser. Connect a wallet and write only that 32-byte hash to the Base Sepolia registry.
Verify forever
Anyone can re-hash the file and check whether the fingerprint exists onchain. No wallet needed. No login. No fee.
When to timestamp a file
A blockchain timestamp is useful any time you want to prove a file existed before an event — publication, collaboration, disclosure, or loss. The hash captures the file's identity at that moment.
Before publishing
Timestamp a draft or dataset before you publish. If someone later claims you copied them, the onchain fingerprint shows your file existed first.
Before sharing with others
Send a file to a collaborator? Timestamp it first. If the relationship sours, you can prove you held the original at a known time.
Before archiving
Timestamp a file before moving it to cold storage or a new format. Years later, verify the content hasn't drifted from the original.
Before regulatory submission
Records, logs, and compliance documents can be timestamped before submission. The onchain record serves as an independent integrity checkpoint.
What a proof means
OpenProof proves
- ✓A specific SHA-256 fingerprint existed in the registry at a recorded block time.
- ✓A specific wallet address submitted that hash for registration.
- ✓A file you hold today produces the same hash (it is unchanged since registration).
OpenProof does not prove
- ✗Who created, owns, or has rights to the file.
- ✗That the file contents are true, accurate, or correct.
- ✗That the file is legally valid or compliant with any regulation.
- ✗Recovery of the original file if it is lost.
0x60d3DD631E6e4F6D76f761689d6FA229945a874aBase Sepolia84532OwnerlessPrivacy by design
No uploads
Files are hashed locally in your browser using the native Web Crypto API. The bytes never leave your device. Only the 32-byte SHA-256 hash leaves your browser — and only when you choose to register it.
No accounts
There is no sign-up, no profile, no database of users. OpenProof has no backend. Your proof history lives in your browser's local storage, not on a server.
Permanent verification
Once a hash is registered on Base Sepolia, it is immutable. Anyone can verify the proof using the onchain record alone — no website, no account, no special software required.
No tracking
OpenProof contains no analytics scripts, no tracking pixels, no cookies, and no telemetry. There is nothing to opt out of because nothing is collected.
OpenProof is proof-of-existence infrastructure. A SHA-256 fingerprint on Base Sepolia. No backend, no database, no tracking. Just a hash onchain.