Learn Simplicity - 10 Code Examples & CST Typing Practice Test

Simplicity is a typed, functional smart contract language designed for blockchain applications, with a focus on formal verification, expressiveness, and secure, predictable execution, primarily targeting Bitcoin and similar blockchain platforms.

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Simplicity Minimal Contract Example Simplicity Basic Escrow Simplicity Time-Lock Contract Simplicity Multi-Signature Wallet Simplicity Conditional Payment Simplicity Atomic Swap Simplicity Escrow with Timeout Simplicity Crowdfunding Contract Simplicity Token Vesting Simplicity Payment Channel

Learn SIMPLICITY with Real Code Examples

Updated Nov 25, 2025

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Code Sample Descriptions

Simplicity Minimal Contract Example

// Define a contract that locks funds until a condition is met
contract lockFunds {
    input: signature sig, condition cond
    output: funds released if cond(sig) == true
}

A minimal example illustrating a composable financial contract in Simplicity.

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Simplicity Basic Escrow

contract escrow {
    input: sig senderSig, sig recipientSig
    output: funds released if verify(senderSig) && verify(recipientSig)
}

Funds are released to a recipient only if both parties sign.

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Simplicity Time-Lock Contract

contract timelock {
    input: currentBlockTime
    output: funds released if currentBlockTime >= lockTime
}

Funds are locked until a specific block time is reached.

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Simplicity Multi-Signature Wallet

contract multisig {
    input: sigs[3]
    output: funds released if count_valid(sigs) >= 2
}

Releases funds only if multiple signatures approve.

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Simplicity Conditional Payment

contract conditionalPay {
    input: sig payerSig, data d
    output: funds released if validate(d) && verify(payerSig)
}

Transfers funds only if a condition on input data is satisfied.

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Simplicity Atomic Swap

contract atomicSwap {
    input: hash preimage, sig senderSig, sig receiverSig
    output: funds released if hash(preimage) == knownHash && verify(senderSig) && verify(receiverSig)
}

Enables atomic swap between two parties using hash preimage.

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Simplicity Escrow with Timeout

contract escrowTimeout {
    input: sig senderSig, sig recipientSig, currentBlockTime
    output: funds released to recipient if verify(recipientSig) || refunded to sender if currentBlockTime >= timeout
}

Funds can be claimed by recipient or refunded after timeout.

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Simplicity Crowdfunding Contract

contract crowdfunding {
    input: sig contributorSig, amount, totalRaised
    output: release to owner if totalRaised >= goal else refundable to contributors
}

Funds are released to project owner only if funding goal is reached.

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Simplicity Token Vesting

contract vesting {
    input: currentBlockTime
    output: release vestedAmount(currentBlockTime) to recipient
}

Vests tokens over time to a recipient.

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Simplicity Payment Channel

contract paymentChannel {
    input: sig senderSig, sig receiverSig, balanceUpdate
    output: settle funds according to signed balanceUpdate
}

Enables off-chain microtransactions with on-chain settlement.

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Frequently Asked Questions about Simplicity

What is Simplicity?

What are the primary use cases for Simplicity?

Formal-verifiable smart contracts. Multi-signature wallets. UTXO-based DeFi primitives. Escrow and payment channels. High-assurance blockchain applications

What are the strengths of Simplicity?

High security due to formal verification. Predictable and auditable execution. Eliminates many common smart contract bugs. Composability allows building complex logic safely. Ideal for financial and payment contracts

What are the limitations of Simplicity?

Steep learning curve. Smaller ecosystem than Solidity or Move. Low-level: less developer-friendly. Limited tooling and IDE support. Primarily targets UTXO blockchains

How can I practice Simplicity typing speed?

CodeSpeedTest offers 10+ real Simplicity code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

Simplicity Minimal Contract Example

// Define a contract that locks funds until a condition is met
contract lockFunds {
    input: signature sig, condition cond
    output: funds released if cond(sig) == true
}

A minimal example illustrating a composable financial contract in Simplicity.

Let’s Try →

Simplicity Basic Escrow

contract escrow {
    input: sig senderSig, sig recipientSig
    output: funds released if verify(senderSig) && verify(recipientSig)
}

Funds are released to a recipient only if both parties sign.

Let’s Try →

Simplicity Time-Lock Contract

contract timelock {
    input: currentBlockTime
    output: funds released if currentBlockTime >= lockTime
}

Funds are locked until a specific block time is reached.

Let’s Try →

Simplicity Multi-Signature Wallet

contract multisig {
    input: sigs[3]
    output: funds released if count_valid(sigs) >= 2
}

Releases funds only if multiple signatures approve.

Let’s Try →

Simplicity Conditional Payment

contract conditionalPay {
    input: sig payerSig, data d
    output: funds released if validate(d) && verify(payerSig)
}

Transfers funds only if a condition on input data is satisfied.

Let’s Try →

Simplicity Atomic Swap

contract atomicSwap {
    input: hash preimage, sig senderSig, sig receiverSig
    output: funds released if hash(preimage) == knownHash && verify(senderSig) && verify(receiverSig)
}

Enables atomic swap between two parties using hash preimage.

Let’s Try →

Simplicity Escrow with Timeout

contract escrowTimeout {
    input: sig senderSig, sig recipientSig, currentBlockTime
    output: funds released to recipient if verify(recipientSig) || refunded to sender if currentBlockTime >= timeout
}

Funds can be claimed by recipient or refunded after timeout.

Let’s Try →

Simplicity Crowdfunding Contract

contract crowdfunding {
    input: sig contributorSig, amount, totalRaised
    output: release to owner if totalRaised >= goal else refundable to contributors
}

Funds are released to project owner only if funding goal is reached.

Let’s Try →

Simplicity Token Vesting

contract vesting {
    input: currentBlockTime
    output: release vestedAmount(currentBlockTime) to recipient
}

Vests tokens over time to a recipient.

Let’s Try →

Simplicity Payment Channel

contract paymentChannel {
    input: sig senderSig, sig receiverSig, balanceUpdate
    output: settle funds according to signed balanceUpdate
}

Enables off-chain microtransactions with on-chain settlement.

Let’s Try →

Frequently Asked Questions about Simplicity

What is Simplicity?

What are the primary use cases for Simplicity?

Formal-verifiable smart contracts. Multi-signature wallets. UTXO-based DeFi primitives. Escrow and payment channels. High-assurance blockchain applications

What are the strengths of Simplicity?

What are the limitations of Simplicity?

Steep learning curve. Smaller ecosystem than Solidity or Move. Low-level: less developer-friendly. Limited tooling and IDE support. Primarily targets UTXO blockchains

How can I practice Simplicity typing speed?

CodeSpeedTest offers 10+ real Simplicity code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.