Build and Test Zero-Knowledge Proof Verification
Free Testnet Environment
Kurier Testnet is a free sandbox for developers building zero-knowledge applications. Submit and verify ZK proofs against live infrastructure — on zkVerify testnet or Base Sepolia — before deploying to mainnet. No cost. No production risk.
Full feature parity with mainnet. New proof types and networks land here first. Read our guide here.
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Built for Developers
Secure
An immutable foundation for your zk-dApp. Proofs are submitted on-chain via zkVerify, providing a tamper-proof audit trail for every verification.
Fast
Optimistic verification delivers near-instant results, with on-chain finality available for applications requiring full cryptographic guarantees.
Simple
A single REST API endpoint replaces the need to run a zkVerify node, manage crypto payments, or write custom proof-submission logic.
Interoperable
Designed to support multiple zk-proof types on various blockchain networks. See the full list of supported networks.
What is Kurier?
Kurier is a REST API built by Horizen Labs that abstracts the complexity of ZK proof submission and on-chain verification. Instead of running your own zkVerify node or managing blockchain infrastructure, you send a proof to the Kurier API and get back verifiable, on-chain results.
Kurier supports all major ZK proof systems in use today — making it the most comprehensive zero-knowledge proof verification API available.
Why Start on Testnet?
Testnet is the recommended starting point for all new Kurier integrations:
Free to use
Testnet API keys and proof submissions have no cost
Full feature parity
Everything available on mainnet is available on testnet first
New features launch here
Testnet gets new proof types, networks, and features before mainnet
Safe integration testing
Validate your proof formats, job polling logic, and callback handling without spending real funds
Once your integration is stable, migrate to mainnet in minutes.
Supported ZK Proof Types
Kurier Testnet supports all of the following ZK proof systems:
groth16
The gold standard for zk-SNARK verification
fflonk
Efficient PLONK-based proofs
plonky2
Fast recursive proofs compatible with Ethereum
risc0
General-purpose verifiable computation via RISC-V zkVM
sp1
Succinct’s high-performance zkVM
ultrahonk
Aztec’s next-generation proving system
ultraplonk
Aztec’s PLONK variant for private smart contracts
proof of SQL
ZK proofs for verifiable database queries
tee
Trusted Execution Environment attestation proofs
Supported Networks on Testnet
zkVerify Testnet
Decentralized ZK-proof verification chain
Base Sepolia
Ethereum L2 testnet by Coinbase
How It Works
Sign up for a free testnet API key at testnet.kurier.xyz
Submit a proof via POST to the Kurier testnet API endpoint
Receive a jobID and poll for real-time verification status
Proof is finalized on-chain on zkVerify testnet or Base Sepolia
Validate your integration, then go to mainnet
Zero-Knowledge Proofs — A Primer
New to ZK proofs? A zero-knowledge proof (ZKP) lets you prove that a computation was done correctly — without revealing any of the data involved. This makes ZK proofs fundamental to:
Private transactions on blockchain
Scalable rollups (zkSync, StarkNet, Polygon zkEVM)
Verifiable AI and ML inference
Trustless identity and credentials
Verifiable database queries (proof of SQL)
Kurier makes it easy to integrate ZK proof verification into any of these use cases via a single API.
Roadmap
Submit a New Feature Request
Q4'25
Q1'26
Q2'26
