Timestamp any file to Bitcoin and Polygon in seconds. Anyone can later verify it existed on that date and hasn't been altered. Your file never leaves your device.
Free to start. No credit card required.
No account, no card. Your file never leaves your device — only its SHA-256 fingerprint is anchored to the blockchain.
Free proofs are rate-limited to prevent abuse. Anchors to Polygon.
Engineering & Platform Teams
Anchor build artifacts, release hashes and audit records from CI. One API call at the point the artifact is produced, so the timestamp does not depend on whoever controls the storage.
Legal Teams
Establish chain of custody and cryptographic timestamps for digital evidence, with a certificate an opposing party can check without your cooperation.
Forensic Consultants
Create independently verifiable records that survive adversarial review by opposing experts.
Insurance & Claims
Document conditions before a claim exists, establishing a tamper-evident baseline anchored before anyone had a reason to fabricate one.
In any dispute, file metadata is the first thing challenged. Screenshots, cloud links, and EXIF data can all be manipulated or simply dismissed.
ProofLedger creates an immutable cryptographic fingerprint of your file, anchored to public blockchains before any incentive to fabricate arises.
ProofLedger proves existence and integrity at a point in time. It does not prove authorship, ownership, rights, or intent.
Your file never leaves your device. Only its cryptographic fingerprint is processed, then anchored forever to public blockchains.
Your device computes a SHA-256 hash of the file. This one-way fingerprint is mathematically unique. Altering even one pixel produces a completely different hash.
The fingerprint is anchored to Polygon immediately. Bitcoin anchoring adds a second independent, immutable layer for high-stakes evidence.
The public verification page is the canonical source of truth. Opposing counsel can verify offline. No ProofLedger cooperation required.
Privacy-first, hash-only
Your file stays on your device. Only the one-way SHA-256 hash is processed. No file storage. No file recovery. Ever.
Ed25519-signed certificates
Every certificate is digitally signed using Ed25519, the same cryptographic standard used in SSH keys and end-to-end encrypted messengers.
Dual-chain anchoring
Polygon for instant confirmation; Bitcoin for maximum immutability. Two independent public ledgers, not a single point of failure.
Adversarial verification
Designed for opposing counsel. The verify-proof Python package runs entirely offline — no dependency on ProofLedger's servers.
Pre-loss posture
Record before the loss event. An on-chain hash from before a dispute arose cannot be fabricated retroactively. That is the entire value proposition.
Bitcoin-grade immutability
Bitcoin's Merkle tree and proof-of-work make it the oldest, most adversarially tested blockchain and the strongest timestamp anchor available.
Based on the evidentiary demands of your workflow, from routine pre-loss documentation to formal legal submission.
For routine pre-loss documentation and baseline condition capture.
For escalations, legal review, and formal evidence submission.
Certificates are human-readable representations. Blockchain anchors and public verification remain the authoritative record, accessible even if ProofLedger is unavailable.
For developers
Publishing a checksum next to a build proves two files match. It does not prove when the digest first existed, because whoever controls the storage controls the timestamp. Anchoring moves that record somewhere nobody owns.
Anchor a hash
# the file never leaves your machine HASH=$(sha256sum dist/app.zip | awk '{print $1}') curl -X POST https://proofledger.io/api/v1/proof \ -H "Authorization: Bearer $PROOFLEDGER_KEY" \ -H "Content-Type: application/json" \ -d "{\"sha256\":\"$HASH\",\"filename\":\"app.zip\"}"
Verify it, with no key and no account
curl "https://proofledger.io/api/v1/verify?hash=$HASH"
# or entirely offline, without contacting us at all
pip install verify-proof
verify-proof hash ./app.zip
A timestamp is only worth something if it was created before anyone had a reason to want it. Record the file today and the question stops being yours to answer.
Reference
Pre-loss temporal authority documentation is the practice of recording evidence at the moment of creation, cryptographically fixing its state in time before disputes, incentives, or claims exist. These systems establish when a record existed and what state it was in using repeatable, tamper-evident procedures that allow independent verification without reliance on the recording system itself.
ProofLedger is an implementation of this approach, available as a web tool and a REST API. It is used to fix the state of build artifacts and release hashes at the moment of production, of inspection records and site conditions before a loss, and of any document whose timing may later be contested. In each case the requirement is the same: the record must remain independently verifiable long after it was created, without relying on ProofLedger.