Clarity 4 is Now LIVE: Making Bitcoin Smart Contracts More Powerful

SIP-033 and SIP-034 have officially activated at Bitcoin block 923222 – bringing Clarity 4 live on Stacks, the smart contract layer secured by Bitcoin.

This upgrade introduces Version 4 of the Clarity smart contract language, marking a major step forward for the Stacks ecosystem. For users, it delivers safer, smarter contracts with enhanced built-in protections. 

For builders, it unlocks five powerful new functions that make developing secure, flexible, and Bitcoin-native DeFi applications easier than ever.

What Clarity 4 Means for Bitcoin Builders

1. On-chain Contract Verification

Developers can now fetch the hash of another contract’s code body.

This makes it possible for one contract to verify that another follows a specific template before interacting with it. This is a major step toward safer, more trustless bridges and marketplaces that support a wider range of assets.

2. Allowing Contracts to Set Post-Conditions

New functions allow contracts to set post-conditions that protect their assets.

This means a contract can safely call external contracts (such as traits) and automatically roll back any changes if the executed code moves assets beyond what’s allowed.

3. Convert Simple Values into ASCII Strings

Clarity 4 adds a function to convert simple values like bool s or principal s into ASCII strings.

This makes it easier to generate readable, string-based messages – a useful tool for developers building cross-chain features and integrations.

4. Get the Timestamp of the Current Block

A new keyword lets developers retrieve the timestamp of the current block.

This addition enables time-based logic in smart contracts – an essential capability for building features like yield schedules, lockups, or expiration conditions in DeFi apps.

5. Native Passkey Integration

Clarity 4 introduces a new function, secp256r1-verify, enabling on-chain verification of secp256r1 signatures.

This lays the groundwork for passkey-based authentication, opening the door to features like hardware-secured wallets and biometric transaction signing.

6. Dimension-specific Tenure Extensions

The SIP-033 vote also included technical rider SIP-034, which introduces dimension-specific tenure extensions. Signers can approve resets to one budget dimension (e.g., read-count) without resetting others, allowing high-throughput workloads even when the cost model is pessimistic.

Why This Upgrade Matters for Bitcoin DeFi

Clarity 4 strengthens Stacks' position as Bitcoin's liquidity layer by giving developers the tools to build more sophisticated Bitcoin DeFi applications – all secured by Bitcoin through Stacks' Proof of Transfer mechanism.

Whether you're building Bitcoin lending protocols, yield products with sBTC, or the next generation of BTCFi applications, Clarity 4 delivers the security and functionality Bitcoin capital markets demand.

Every transaction on Stacks settles on Bitcoin. That's Bitcoin-level security with the flexibility of smart contracts.

Start Building on Bitcoin Today

Ready to unlock Bitcoin liquidity with Clarity 4? Check out the full SIP-033 & SIP-034 specifications and join over 1000 developers building where Bitcoin grows.

To start building Bitcoin-native apps, explore Clarity 4 Documentation →