Extended UTxO
Cardano’s eUTxO model takes Bitcoin’s proven foundation and adds three powerful ingredients: Datum, Redeemer, and Context.
Datum
Custom data attached to script-locked outputs. This is the “state” of a smart contract, think of it as a note pinned to a banknote that says what it’s for.
Redeemer
Data provided by the person spending the output. It’s the “action” or argument passed to the validator: claim, swap, vote, cancel, whatever the contract expects.
Script Context
The full transaction visible to the validator script. Inputs, outputs, fees, signatories, time range, everything needed to decide if this spend is valid.
datum
context
→ True | False
new datum
Determinism Preserved
The critical advantage: because the script sees only the transaction (not global state), validation is fully deterministic. You know whether your transaction will succeed before you submit it. With honest pre-validation, transactions don’t fail on-chain unexpectedly, and if a script does fail in phase-2 validation, only the dedicated collateral is consumed, not the full transaction value.
Validator Playground
Explore how an eUTxO validator evaluates a transaction. Configure the inputs and see the result.
The Road to eUTxO
Bitcoin launches with UTxO
Satoshi introduces the UTxO model: simple, robust, designed for decentralized value transfer.
Ethereum introduces Accounts
Vitalik chooses accounts to enable richer smart contracts. Trade-off: shared mutable state.
eUTxO Paper published
Chakravarty et al. formalise an extension of UTxO that supports expressive contracts while preserving the dataflow properties of the original model.
Alonzo hard fork
Cardano brings eUTxO smart contracts to mainnet with Plutus scripts.
Ecosystem matures
Design patterns emerge: CEM, multi-validator protocols, batch processing at scale.
Three quick questions
Optional. Score 3/3 to earn mastery badges. Your first attempt counts for the Polymath badge. Questions and answer order are randomised on every attempt.
