Crypto.org Chain JS library is a JavaScript SDK for building and signing transactions on the Crypto.org blockchain, along with querying chain data. The library provides functionality for key management (mnemonic phrases, HD key derivation, key pairs), address generation, transaction construction and signing, transaction encoding and decoding, offline signing workflows, and blockchain queries. Built with JavaScript and TypeScript, it integrates with CosmJS for transaction broadcasting and chain queries, uses Secp256k1 for cryptographic operations, and supports Protobuf for transaction serialization. The project is maintained by Crypto.org and contributors, though it is explicitly marked as alpha and not production-ready.