Overview
Buildooor is a free code library that helps developers assemble blockchain transactions inside their own apps. A transaction is the signed message that moves ADA, creates tokens, or records a vote, and it only works if the fee, balances, and format are exactly right. Buildooor handles that bookkeeping, a bit like tax software that fills in the forms and does the arithmetic once you enter the numbers.
The library builds transactions for Cardano and is written in TypeScript, the typed version of JavaScript used across many web apps. It ships as an npm package (npm is the public registry JavaScript developers use to share code) under the Apache 2.0 open-source license1. It comes from Harmonic Labs, a development studio that also created plu-ts, a TypeScript toolkit for writing smart contracts (programs that run on a blockchain)2.
Key Features
- Transactions written as a list of steps. Developers chain plain instructions such as pay this address, mint these tokens, delegate to this stake pool, or attach a note, then call one build step to get a finished transaction3.
- Fees and minimum balances worked out automatically. Buildooor's builder calculates the network fee, adds the minimum ADA each output (each amount the transaction sends to an address) must carry, and checks that leftover funds return to a change address4.
- Smart contract costs measured before sending. When a transaction uses a Plutus script (a Cardano smart contract), Buildooor runs the script locally to measure how much computing it needs and adds that cost to the fee4.
- Governance actions from code. Apps can cast votes as a DRep (a delegated representative who votes for ADA holders), a stake pool, or a constitutional committee member, and file proposals such as treasury withdrawals3.
- Choice of data provider. A provider interface defines how Buildooor looks up funds, reads network settings, signs, and submits, so developers can connect any data service that implements it5.
What to Expect
Buildooor is a tool for developers, not an app for everyday users, and people using an app built on it never see it directly. For developers, setup is a single npm install command, which the GitHub README shows6. The source code and test files show how each piece fits together, from simple payments to multi-signature transactions, which need more than one signer, and script transactions7.
Harmonic Labs uses Buildooor inside its own tools. Pebble, the team's smart contract language, lists it as a dependency8. The team's kupmios-pluts package connects to the Kupo and Ogmios network services and returns data ready to pass into Buildooor's builder9.
Outside the team, ODATANO, a service that opens Cardano up to business software through the OData data standard, builds its transactions with Buildooor10. Developers comparing options in other programming languages can browse the wider set of transaction builders.
