Learn SIMPLICITY with Real Code Examples

Simplicity is low-level and strongly typed, designed to eliminate common programming errors found in Bitcoin Script and Solidity.

It supports formal verification, allowing developers to mathematically prove contract correctness before deployment.

Contracts are built from composable expressions and functions, ensuring predictable behavior.

It targets UTXO-based blockchains like Bitcoin and Elements, enabling safer financial operations.

Used in high-assurance financial applications, multi-signature schemes, and complex blockchain logic where correctness is critical.

Expressions instead of statements

Function combinators for building contracts

Typed value system

Integration with Bitcoin/Elements UTXO model

Support for cryptographic primitives and verification

Expressions and combinators instead of traditional statements

Typed values and type-safe functions

No loops or unbounded recursion

Purely functional and deterministic execution

Integration with UTXO transaction model

src/ - Simplicity combinator definitions

tests/ - verification and unit tests

scripts/ - transaction scripts

build/ - compiled bytecode

docs/ - formal proofs and contracts documentation

Write contract using Simplicity combinators

Compile to AST and then to bytecode

Optionally prove correctness using formal verification

Deploy bytecode via UTXO blockchain transaction

Interact with contract using transaction scripts

Beginner: simple multi-sig

Intermediate: payment channels

Advanced: UTXO-based DeFi primitive

Expert: formally verified financial contract

Auditor: verify correctness proofs and safety

Simplicity vs Bitcoin Script: typed, verifiable, composable vs low-level and limited

Simplicity vs Solidity: more verifiable and low-level, less user-friendly

Simplicity vs Vyper: functional and typed vs minimalistic EVM language

Simplicity vs Move: UTXO-focused vs account/resource-focused

Simplicity vs Haskell smart contracts: Simplicity is blockchain-focused and deterministic

2015 – Concept of Simplicity introduced

2016 – Initial prototype development

2017 – Reference implementation release

2018–2020 – Formal verification tools integrated

2021–2025 – Ongoing research and ecosystem experiments

UTXO: unspent transaction output

Combinator: functional building block

AST: abstract syntax tree

Bytecode: serialized contract for blockchain

Formal verification: proving contract correctness