Spend validators control the conditions under which UTXOs can be spent from script addresses.
Real-world Use Cases
Asset Locking: Define conditions for when locked assets can be accessed
Multi-signature Schemes: Require approval from multiple parties
Time-locked Funds: Allow access only after certain time conditions
Conditional Payments: Release funds when specific on-chain/off-chain conditions are met
Required UTxO Fields and Deployed Blueprint
PREREQUISITE: DEPLOYED SMART CONTRACT
Before you can interact with any validator, you must have a compiled and deployed smart contract blueprint. The validator hash used in these examples comes from your deployed blueprint.
Refer to the guide for details on how to deploy your smart contract blueprint.
Don't forget to lock assets at the script address in a prior transaction. Then when spending, specify the locked UTxO using the outputRef field, which pinpoints the UTxO by its transaction hash and output index.
{
"txHash": "transaction_hash", // Transaction hash where funds were locked
"index": 0 // Output index within that transaction
}
Anvil API returns the UTXOs in the order they were added when you previously locked the assets.
Spend Validator API Interaction Example
Use the below examples to build transactions that interact with the spend validator.
1. Locking Assets at Script Address
// Build a transaction to lock funds at a script address
const lockInput = {
// Address where change outputs will be sent (your wallet address)
changeAddress: "ADDR_YOUR_CHANGE_ADDRESS",
// Optional message for transaction metadata (appears in block explorers)
message: "Locking funds using the spend validator",
// UTxOs to use as inputs (hex-encoded transaction outputs)
// These provide the funds being locked at the script address
utxos: [
"8282...", "8282...", "8282...", "8282..."
],
// Outputs to create in this transaction
outputs: [
{
// Script address derived from validator hash
address: scriptAddress,
// Amount of lovelace (unit of ADA) to lock at script address
lovelace: LOVELACE_AMOUNT,
// Datum stores information needed for future spending
datum: {
// Stored directly on-chain (vs. hash-only)
type: "inline",
// The actual datum content as specified by your validator's blueprint
value: {
owner: "addr_test1xyz...", // Owner's verification key hash who can unlock
},
// References validator hash and purpose for serialization
shape: { validatorHash, purpose: "spend" }
}
}
]
};
2. Spending (Unlocking) Locked UTxO
// Build a transaction to spend (unlock) funds from the script address
const unlockInput = {
// Address where unlocked funds will be sent (your wallet address)
changeAddress: "ADDR_YOUR_CHANGE_ADDRESS",
// Optional message for transaction metadata (appears in block explorers)
message: "Unlocking funds using the spend validator",
// UTxOs to use for transaction fees and collateral
// These are regular wallet UTxOs, not the script UTxO being spent
utxos: [
"8282...", "8282...", "8282...", "8282..."
],
// Define how to interact with smart contract validators
scriptInteractions: [
{
// Validator script hash (matches one used when locking funds)
hash: validatorHash,
// We're using the spend validator
purpose: "spend",
// Points to the specific UTXO at the script address we want to spend/unlock
outputRef: {
txHash: "TRANSACTION_HASH", // Transaction hash where funds were locked
index: 0 // Output index within that transaction
},
// Redeemer provides arguments to the validator
// Here we're unlocking the funds with a simple message defined in the smart contract
redeemer: {
type: "json",
value: {
msg: "hex-encoded-message"
}
}
}
],
// Transaction must be signed by these key hashes
// Often matches owner key from the datum to verify authorization
requiredSigners: [signerKeyHash]
};
See Examples
If you are unfamiliar with the Anvil API transaction builder, review the guide first.
