CertVera has launched a new L402-powered API that lets anyone — developers, businesses, or AI agents — timestamp document hashes on the Bitcoin blockchain. No accounts. No API keys. Just a Lightning wallet.
What Is L402?
L402 is an HTTP-native payment protocol built on top of Bitcoin's Lightning Network. Instead of traditional authentication (API keys, OAuth tokens, sessions), L402 uses Lightning invoices as access tokens. The flow is simple:
- Request — Send a POST to the API
- Pay — Receive an HTTP 402 response with a Lightning invoice
- Prove — Pay the invoice, then retry with the preimage as your credential
This means any software that can pay a Lightning invoice can use CertVera — no signup required.
The Timestamp Endpoint
Our primary endpoint anchors SHA-256 hashes into Bitcoin transactions using OP_RETURN outputs. Here's how it works:
POST https://certvera.com/api/l402
Content-Type: application/json
{"action": "l402_timestamp", "hash": "e3b0c44298fc1c149afbf4c8996fb924..."}The API responds with a Lightning invoice. Once paid, your hash is queued for the next Bitcoin block. You get back a timestamp_id that you can use to track confirmation status.
Dynamic Pricing
Each timestamp requires an on-chain Bitcoin transaction, so pricing adjusts with network conditions:
- Service fee: 20,000 sats (fixed)
- Network fee: Varies with Bitcoin mempool congestion
- Typical total: 25,000–35,000 sats
- Maximum: 250,000 sats (extreme congestion only)
The exact price is always shown in the Lightning invoice before you pay — no surprises.
Free Verification, Forever
Once a hash is timestamped, verification is completely free. Anyone can check whether a document hash exists on the blockchain:
POST https://certvera.com/api/l402
Content-Type: application/json
{"action": "l402_timestamp_verify", "hash": "e3b0c44298fc1c149afbf4c8996fb924..."}The response includes the Bitcoin transaction ID, block height, confirmation count, and the exact timestamp — everything needed for independent verification.
Built for AI Agents
One of the most exciting aspects of L402 is that it's inherently agent-friendly. Traditional APIs require developers to create accounts, generate keys, and manage credentials. L402 removes all of that friction.
Any AI agent with access to a Lightning wallet can:
- Timestamp outputs for auditability
- Prove that a report or analysis existed at a specific time
- Create immutable records without human intervention
- Integrate via standard HTTP — no SDKs or libraries needed
CertVera is listed in the Lightning Faucet L402 Registry, making it discoverable by agents that browse available L402 services.
Use Cases
Legal documents — Timestamp contracts, agreements, or evidence to establish when they existed.
Creative works — Prove authorship dates for music, writing, code, or artwork.
Prior art — Establish dated records of inventions before filing patents.
Compliance — Create audit trails with immutable, third-party-verifiable timestamps.
AI accountability — Anchor agent outputs so they can be independently verified later.
Getting Started
Timestamping your first document takes about 30 seconds:
- Hash your file locally:
sha256sum document.pdf - Submit the hash to our API
- Pay the Lightning invoice
- Done — your proof of existence is on Bitcoin
No account creation. No email verification. No waiting for API key approval.
Read the full API documentation to get started, or try the interactive verification tool to look up an existing timestamp.
CertVera is built and operated by the team behind Lightning Faucet. Questions? Reach us at hello@certvera.com.