The Bitcoin Dev Kit: WebAssembly

The Bitcoin Dev Kit for Browsers, Node, and React Native

About

The bdk-wasm library aims at providing access to the excellent BitcoinDevKit to JS and Node environments (and eventually any device supporting WebAssembly). It specializes in compiling BDK on the wasm32-unknown-unknown target and use wasm-bindgen to create TypeScript bindings.

This repo handles the packaging and publishing of the bdk-wallet-web (for browsers) and bdk-wallet-node (for Node.js) NPM packages, using wasm-pack.

This library offers all the desired functionality to build a Bitcoin wallet out of the box:

• UTXO management
• Coin selection
• Wallet upates by syncing and scanning the chain data
• Bitcoin descriptors for flexibility in the definition of spending conditions. Supports all address types from legacy to Taproot.
• State update and persistence
• Transaction creation, signing and broadcasting
• Dynamic addresses
• and much more

For a lightweight library providing stateless utility functions, see bitcoinjs.

Installation

Browser/Web

yarn add @bitcoindevkit/bdk-wallet-web

Node.js

yarn add @bitcoindevkit/bdk-wallet-node

Notes on WASM Specific Considerations

[!WARNING] There are several limitations to using BDK in WASM. Basically any functionality that requires the OS standard library is not directly available in WASM. However, there are viable workarounds documented below. Some key limitations include:

• No access to the file system
• Network access is limited to http(s)

WASM Considerations Overview

No access to the file system

With no direct access to the file system, persistence cannot be handled by BDK directly. Instead, an in memory wallet must be used in the WASM environment, and the data must be exported using wallet.take_staged(). This will export the changeset for the updates to the wallet state, which must then be merged with current wallet state in JS (will depend on your persistence strategy). The persisted ChangeSet can be passed to wallet.load() to recover the wallet.

Network access is limited to http(s)

This essentially means the library only supports Esplora as blockchain client. Both RPC and Electrum clients require sockets and will not work for BDK in a WASM environment out of the box.

Development Environment

Requirements

• Install Rust
• Install wasm-pack

MacOS special requirement

Refers to this section.

Build with wasm-pack build

[!IMPORTANT] You need the wasm32-unknown-unknown toolchain to be installed:

rustup target add wasm32-unknown-unknown

To build for browser/web:

wasm-pack build --target bundler --features "esplora"

To build for Node.js:

wasm-pack build --target nodejs --all-features

Test in Headless Browsers with wasm-pack test

wasm-pack test --headless --firefox

Works with --firefox, --chrome or --safari.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.