クライアントライブラリ & SDK (フロントエンド)

Web3j is the Java and Android integration library for Ethereum. Created in 2016, and still going strong in 2025 it is core plumbing to Ethereum for one of the world's most widely used development platforms, the JVM. It has been downloaded millions of times, and is used by everyone including Enterprises such as J.P. Morgan, Fnality and NTT Data Web3 infrastructure companies such as Alchemy The Besu Ethereum Execution client It's even been integrated natively into the Android OS by Freedom Factory in ethOS which powers the upcoming Ethereum phone the DGEN1 We decided in 2024 to bring Web3j into the Hyperledger Foundation, which provides high-quality governance of open source (similar to the Apache Foundation). It's still, the same team at Web3 Labs responsible for maintaining and supporting the library for its wide and varied user base. The Hyperledger association is great for visibility, but doesn't provide any funding for the project! We rely on grant funding to sustain this library and hopeful to qualify for this RPGF round. Unfortunately, we missed out on OP RPGF 3 as we had not realised projects were eligible for multiple rounds so did not apply following our success in OP RPGF 2. 🙏🏻

Viem is the most used modern TypeScript Interface for Ethereum. Viem provides robust, performant, and type-safe modules to be the foundation for building Web Applications, TypeScript Libraries, Wallets, Backends, Indexers, Scripts, and more, on top of Ethereum (and the OP Stack). With over 3 million monthly downloads, Viem is used in production by most at-scale projects like Coinbase, Uniswap, Optimism, Polymarket, Zora, Opensea, WalletConnect, Farcaster, Rainbow, and so much more.

web3.py is the open source library that connects Python developers to Ethereum. The same team maintains more than a dozen additional building blocks including py-evm, eth-account, and eth-utils.