> For the complete documentation index, see [llms.txt](https://docs.orbisprotocol.com/orbis/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.orbisprotocol.com/orbis/technology/cardano/eutxo.md). # EUTXO Like Cardano, Orbis uses the EUTXO (Extended Unspent Transaction Output) accounting model for its transactions, an extension of the standard UTXO model enabling expressive smart contracts while keeping the semantic simplicity of the UTXO model. ![Extended UTXO Model](/files/sBVWyaradNdJyYK7H9N5) In a UTXO model, the coin transfer is recorded in a directed acyclic graph with the nodes representing transactions and the edges representing transaction outputs. Wallets keep track of a list of unspent outputs associated with all addresses owned by the user and calculate the users’ balance. * A UTXO is the output of a previous transaction. * UTXO chains don’t have accounts. Instead, coins are stored as a list of UTXOs, and transactions are created by consuming existing UTXOs and producing new ones in their place. * Balance is the sum of UTXOs controlled by a given address. * UTXOs resemble cash in that they use ‘change’, and are indivisible (UTXOs are used whole). The extended UTXO model gives Orbis the ability to run smart contracts safely while maintaining high scalability. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.orbisprotocol.com/orbis/technology/cardano/eutxo.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.