Overview
The Cardano JS SDK is a free code toolkit that lets web developers build wallets and apps that create, sign, and send blockchain transactions. An SDK (software development kit) is a box of ready-made building blocks, so a team can skip writing the low-level plumbing. Wallet makers and DApp (decentralized app) teams use it inside websites, browser extensions, and server programs.
Input Output builds and maintains the Cardano JS SDK as open-source code under the Apache 2.0 license1. It is written in TypeScript, a stricter form of JavaScript, and runs both in web browsers and in Node.js, a common way to run JavaScript on servers1. Developers install it from npm, the main public registry of JavaScript code, where it is split into separate packages such as @cardano-sdk/core2. The Lace wallet was developed hand-in-hand with the SDK and uses it3.
Key Features
- Build Cardano transactions without the low-level code. The tx-construction package gives developers high-level building blocks for assembling transactions, the records that move ADA and tokens between addresses4.
- Automatic choice of which funds to spend. Cardano balances are held as separate chunks, a bit like bills in a physical wallet. The input-selection package picks which chunks to spend, following the CIP-2 coin selection proposal, and handles native tokens too5.
- Keys that stay on a hardware wallet. The Cardano JS SDK Trezor package signs transactions on the device itself, so private keys never leave it6. A separate package covers Ledger devices7.
- Website-to-wallet connections. The dapp-connector package provides TypeScript types and tools for CIP-30, the shared standard that lets a website talk to a user's browser wallet, and adds helpers for remembering which sites a user has allowed8.
- Parts for building a browser wallet. The web-extension package supplies components that manage wallets, store wallet data, and coordinate signing, the core pieces behind a browser wallet9.
What to Expect
For developers, the Cardano JS SDK is a code library, not an app with screens. You install only the packages you need and write your own program around them. The documentation site is an API reference, a catalog of the functions and types each package offers, rather than a step-by-step course10.
The repository's getting-started guide explains the project's two halves. Client libraries run inside your app. Cardano-services is a backend you can host yourself: a server that looks up blockchain data and submits transactions over the web, plus a chain follower that copies on-chain data into a PostgreSQL database. The quick start runs these services on a Cardano test network using Docker, a tool that packages software into self-contained containers11.
For everyday Cardano users, the SDK stays behind the scenes. Lace's code depends on the SDK's packages for keys, hardware wallets, and transaction building12.
The Lace team describes this transaction builder as covering a DApp connector, coin selection, and deriving addresses, and notes that each package ships with its own test suite3.
