Blockchain API and Web services

• Insight (⭐1.2k)

• BTC Connect - Unified Bitcoin Layer-1 and Layer-2 wallet connection and account abstraction.

Playgrounds

• Bitcore Playground

Utilities

• BackPoW - Solo block odds, cost of production and break-even electricity per rig, from live difficulty.

Additional Resources

• LearnBitcoin.com - Bitcoin-only education: a guided six-chapter journey, 17 long-form rabbit holes, and a ~470-entry glossary, CC-BY-SA with no ads or affiliates.

Playgrounds

• Raw transaction decoder - Paste a raw Bitcoin transaction (legacy, SegWit or Taproot) and see every byte named: scripts disassembled, addresses derived, witness and sequence fields explained. Runs in the browser, no server.

Read

• Bitcoin Book of BIPs - Deployed and complete BIPs (⭐11k), grouped by theme. PDF, ePUB, and web.

Blockchain dump

• nodsig (⭐0) - Turns your node's blocks into sealed local artifacts: chain questions become offline lookups, and every answer carries a fingerprint anyone can recompute. Python stdlib only.

Blockchain API and Web services

• OnFinality - Bitcoin RPC endpoints and API access for dApps, wallets, analytics, and backend services.

Utilities

• Freedom Clock - Bitcoin-aware FIRE calculator with sell, borrow, and borrow-then-sell spend models. Converts savings and BTC holdings into years of financial freedom. Fully local, no account, MIT. Also an open-source e-ink desk device (~$30).

Additional Resources

• Bitcoin Institute - Bilingual (EN/JP) archive of Satoshi Nakamoto primary sources: forum posts, emails, and mailing-list messages, each linked to its original source.

Utilities

• dont-trust-verify - Bitcoin-only client-side tools and self-custody education: 22 calculators, validators and decoders (BIP-39 validator, tx-stuck checker, fee estimator, wallet installer SHA-256 verifier, self-custody score quiz), plus primary-sourced guides and hardware wallet reviews. No signup, no tracking, EN + TH.

Utilities

• CryptoCalk - Bitcoin profitability and on-chain calculators: ASIC/GPU mining ROI, hash rate converter, halving countdown, Mayer Multiple, Stock-to-Flow (S2F), Rainbow chart, profit/loss, DCA simulator, tax estimator, liquidation price. Client-side, no signup, available in 6 languages.

Additional Resources

• BitcoinCompanies - Corporate Bitcoin treasury map and leaderboard with claimed vs verified holdings.

Utilities

• Bitcoin Bottom Score - Real-time Bitcoin cycle bottom probability tracker. Aggregates 25 on-chain and macro signals (MVRV Z-Score, Puell Multiple, Hash Ribbon, ETF flows) into a daily P(bottom) score. Free, updated twice daily.

• Lightning Memory (⭐9) - Open-source memory layer for AI agents in the Bitcoin/Lightning economy. L402 payment gateway, vendor reputation, spending anomaly detection.

Market Data API

• CoinGapRadar - Real-time crypto premium tracker across 9 countries. Monitor kimchi premium and regional price gaps. Free, no signup.

• PreReason - Pre-analyzed Bitcoin market briefings via REST API. Covers BTC price, hash rate, difficulty, mining production costs, treasury holdings (30 public companies), and macro signals that move Bitcoin (Fed balance sheet, M2, Treasury yields). Returns trend direction, confidence scores, and regime classification instead of raw numbers. Free tier available.

C++ Libraries

• Libbitcoin

JavaScript Libraries

• toll-booth (⭐2) - HTTP 402 payment middleware for Node.js; gates any API behind Lightning, Cashu, or stablecoin payments with five backend options.

Java Libraries

• bech32 (⭐1) - Bech32 and Bech32m encode/decode library.

Additional Resources

• Bitcoin.diy - Bitcoin-only education and hardware wallet reviews, focused on self-custody for beginners and intermediate users.

Utilities

• PaperVault (⭐65) - Offline paper-based secret storage using AES-256-GCM and Shamir's Secret Sharing. Create printable encrypted backups of seed phrases with threshold key splitting.

Market Data API

• CoinPaprika Free crypto market data API. 12,000+ coins, 350+ exchanges, tickers, OHLCV, historical prices. No API key for free tier.

C Libraries

• UltrafastSecp256k1 (⭐57) - High-performance secp256k1 engine with a stable C ABI, CPU, CUDA, OpenCL, embedded, and WebAssembly targets.

Utilities

• SuperScalar MCP (⭐0) - MCP server for SuperScalar Bitcoin Lightning channel factories — onboard N users in one shared UTXO, no soft fork required.

Utilities

• BTC Airgap Bridge (⭐4) - 100% client-side tool for broadcasting signed Bitcoin transactions from air-gapped wallets.

Additional Resources

• Knowing Bitcoin - Comprehensive Bitcoin education with 214+ in-depth guides on Lightning Network, wallets, security, privacy, and nodes.

Utilities

• Mining visualization

• Bitcoin Serverless Donations (⭐4) - Self-custodial serverless donation widget with address rotation derived from an XPUB.

• Chartscout - Real-time BTC chart pattern detection and trading alerts across multiple exchanges.

Blockchain API and Web services

• Bitview - An open source Bitcoin Core data extractor and visualizer (aka FOSS Glassnode)

Market Data API

• CoinMetrics.io JSON REST API (free as well as paid) with access to market data. Also CSV data file download available.

Wallets API

• BitGo

Open Source Wallets

• Blue Wallet

• Wasabi Wallet

C++ Libraries

• Libbitcoin - A set of cross platform C++ libraries for building bitcoin applications

Additional Resources

• Bennet.org - Interactive technical guides for bitcoiners.

Rust Libraries

• Bithoven (⭐43) - A High-Level, Imperative Language for Bitcoin Smart Contracts, featuring an LR(1) parser with static analysis for compile-time safety.

Playgrounds

• Bithoven IDE - Web IDE for Bithoven, A High-Level, Imperative Language for Bitcoin Smart Contracts.

Utilities

• BTC Tooling (⭐34) - Bitcoin dashboard with real-time price data, a chart, orderbook, market summary, Twitter/X insights, and halving countdown data. Live Demo

Blockchain API and Web services

• Maestro - A high-performance Bitcoin RPC and UTXO indexer API that powers applications with real-time blockchain data, mempool monitoring, and event notifications.

Privacy projects

• Joinmarket (⭐827) - Decentralized CoinJoin implementation

• Jam - User friendly frontend for Joinmarket

JavaScript Libraries

• bitcoin-sdk-js (⭐39) — Bitcoin TypeScript/JavaScript Library for NodeJS, Browser and Mobile. Segwit & Taproot support.

Python Libraries

• pybtc (⭐13) - Python BTC is an experimental project that aims to provide human-friendly interfaces for common BTC operations.

Open Source Wallets

• Sparrow

Blockchain API and Web services

• mempool.space - Open source and self hostable REST, WebSocket and Electrum RPC API

Open Source Wallets

• Green

Blockchain Explorers

• mempool.space - Open source, self hostable blockchain, mempool and lightning network explorer

Rust Libraries

• Bitcoin Dev Kit (BDK) - With BDK, you can seamlessly build cross platform mobile wallets

• Rust Bitcoin (⭐2.7k) - support for de/serialization, parsing and executing on data-structures and network messages.

• Lightning Dev Kit (LDK) - Complete Lightning implementation packaged as an SDK

Full nodes

• Bitcoin Core - direct descendant of the original Bitcoin implementation in C++

Additional Resources

• Learn me a Bitcoin - Greg Walker - extensive learning resource for bitcoin developers

Additional Resources

• Svrgnty.com: Everything Bitcoin A curated list of the best Bitcoin resources.

Open Source Wallets

• Coin Wallet

Blockchain API and Web services

• Tatum - The blockchain development platform to build Web3 application. The go-to blockchain data API for Web3 developers.

Blockchain API and Web services

• Bitquery.io - Bitquery provides blockchain data, offering real-time streaming APIs for 40+ chains, NFT APIs, and a money flow investigation tool.

Haskell Libraries

• Haskoin-core (⭐535) - Haskoin Core is a library of Bitcoin and Bitcoin Cash functions written in Haskell.

Read

• A Gentle Introduction to Bitcoin Core Development

Additional Resources

• @lopp / Lightning Developers - Software developers with experience working on LN implementations / applications.

Blockchain Explorers

• 3xpl.com - Fastest ad-free universal block explorer.

• Blockchair.com - Universal blockchain explorer and search engine.

Blockchain API and Web services

• Cryptocurrency Alerting - Bitcoin wallet monitoring and blockchain alerts.

JavaScript Libraries

• noble-curves (⭐960) — audited implementation of secp256k1 + schnorr in pure typescript

• noble-secp256k1 (⭐890) — alternative implementation of secp256k1: size is only 4KB gzipped; lots of comments, very valuable for learning how algorithms work

C Libraries

• libsecp256k1 (⭐2.5k)

Ruby Libraries

• bitcoinrb (⭐67) - Ruby bitcoin library including script interpreter.

• bech32rb (⭐22) - Bech32 and Bech32m encode/decode library.

• bip-schnorrrb (⭐8) - Schnorr signature library for Bitcoin.

Swift libraries

• secp256k1.swift (⭐157) - Swift package for secp256k1 applications, includes Elliptic Curve operations, Schnorr, ZKP and more for Bitcoin.

JavaScript Libraries

• scure-btc-signer (⭐242) — audited & minimal library for creating, signing & decoding Bitcoin transactions. With Schnorr, Taproot, UTXO & PSBT.

Blockchain API and Web services

• 3xpl.com - Fastest ad-free universal block explorer.

• blockchair.com - Universal blockchain explorer and search engine.

Utilities

• <qr-code> – A no-framework, no-dependencies, customizable, animate-able, SVG-based <qr-code> web component.

Playgrounds

• ChainQuery Bitcoin RPC - Run select bitcoin RPC API calls and read full RPC docs in your browser.

Playgrounds

• Bitauth IDE – An interactive development environment for Bitcoin contracts.

JavaScript Libraries

• Libauth – A lightweight, zero-dependency, JavaScript/TypeScript bitcoin library.

Blockchain dump

• Chaingraph (⭐60) – A multi-node blockchain indexer and GraphQL API.

Java Libraries

• Bitcoin Spring Boot Starter (⭐85) - Bitcoin integration for Spring Boot applications.

Full nodes

• Fullnode (⭐193) - Javascript implementation of bitcoin.

.Net Libraries

• NBitcoin (⭐1.9k) - Comprehensive Bitcoin library for the .NET framework.

Additional Resources

• River Learn A collection of educational resources to learn about Bitcoin basics, investing, technology, and more.

Utilities

• Nigiri (⭐331) - CLI to quickly fire up a a Bitcoin regtest box along with Electrs and Esplora. Includes faucet and push commands.

• hal (⭐216) - Bitcoin CLI swiss-army-knife (based on rust-bitcoin).

Blockchain API and Web services

• Esplora (⭐1.3k) - Self-hosted blockchain explorer.

Blockchain Explorers

• Blockstream.info - Blockchain explorer with API (mainnet, testnet and Liquid).

Full nodes

• btcd (⭐6.7k) - Go-based full node since 2013.

Python Libraries

• bitcoin_tools (⭐313) - Python library for building and analyzing transactions and scripts (both standard and custom). Comes along with a UTXO set analysis tool. Includes several examples and exhaustive documentation.

Additional Resources

• bitcoin-resources.com Meta-list of Bitcoin resources, from books, articles, to podcasts.

• Jameson Lopp Bitcoin Resource List Very detailed curated Bitcoin resource list and meta-list by J. Lopp

Market Data API

• Messari.io JSON REST API (free as well as paid) with access to market data, news, metrics, profile, etc.

Read

• btcinformation.org / Developer Documentation - Find useful resources, guides and reference material for developers.

Course

• Bitcoin & Cryptocurrency.

Additional Resources

• @lopp / Bitcoin Developers - Software developers who have experience working on Bitcoin implementations or applications.

• A brief history of Bitcoin development...

Utilities

• BitKey - Live USB for airgapped transactions and Bitcoin swiss army knife.

• Pycoin (⭐1.4k) - Python-based Bitcoin and alt-coin utility library.

• bx (⭐643) - Bitcoin Command Line Tool.

• txwatcher (⭐50) - A little Python utility that lets you monitor Bitcoin addresses through Blockchain Websocket API and perform custom callbacks.

• hellobitcoin (⭐255) - A collection of simple programs which can generate bitcoin wallets, create and sign transactions, and send transactions over the bitcoin network.

• HD Wallet Scanner (⭐36) - Find all used addresses in your Bitcoin HD wallets bypassing gap limits.

Blockchain API and Web services

• Chainradar API (⭐5) - Blockchain Explorer API for Chainradar.

JavaScript Libraries

• bcoin (⭐3.1k) - Javascript bitcoin library for node.js and browsers.

Python Libraries

• btctxstore (⭐11) - Simple library to store/retrieve information in bitcoin transactions using OP_RETURN.

• pybitcointools (⭐1.3k) - Python library for Bitcoin signatures and transactions from Vitalik Buterin. Project discontinued.

• pycoin (⭐1.4k) - Python library for Bitcoin keys, signatures, transactions. Includes full VM implementation and tools for manipulating keys (ku) and transactions (tx).

Java Libraries

• XChange (⭐4.1k) - Library that provides a simple and consistent API for interacting with 50+ Bitcoin currency exchanges.

Scala libraries

• Bitcoin-S - Scala/JVM toolkit for Bitcoin applications, includes Bitcoin data structures, transaction signing, strongly typed bitcoind/Eclair RPC clients, and more.

.Net Libraries

• BitcoinLib (⭐413) - The most complete, up-to-date, battle-tested .net Library and RPC Wrapper for Bitcoin and Altcoins in C#.

Playgrounds

• Bitcoin IDE (⭐221) - Bitcoin Script for dummies.

• blockchain-demo (⭐5.7k) - A web-based demonstration of blockchain concepts.

• Bitcoin Script Debugger (⭐60) - Visualize Bitcoin script execution for real transactions.

Blockchain dump

• BitcoinDatabaseGenerator (⭐127) - A high performance data transfer tool that can be used to copy data from Bitcoin Core blockchain files to a SQL Server database.

• Blockparser+SQL (⭐61) - Fast, quick and dirty bitcoin blockchain parser.

• BitcoinABE (⭐977) - Abe: block browser for Bitcoin and similar currencies.

Full nodes

• Bitcoin-ruby-node (⭐26) - bitcoin node based on bitcoin-ruby-blockchain.

• Bitcore Node (⭐352) - bitcoind linked to node.js by BitPay.

• Bitcore (⭐5k) - Formerly just a Nodejs library, now a full node.

Read

• Grokking Bitcoin - An in-depth technical book with rich illustrations.

• Elliptic Curve Cryptography A Gentle Introduction.

• Bitcoin Programming with BitcoinJS and Bitcoin Core CLI (⭐163).

• Bitcoin Protocol Development Curriculum - Chaincode Labs (⭐704).

• Lightning Network Protocol Development Curriculum - Chaincode Labs (⭐372).

Additional Resources

• Practical Bitcoin Info - Google Sheets.

Blockchain API and Web services

• One-Time Address (⭐82) - A better way to share your Bitcoin address.

Blockchain API and Web services

• BlockCypher

• Coinbase Wallet

Wallets API

• Blockchain.com

Blockchain Explorers

• Blockchain.com

JavaScript Libraries

• Bitcore Library (⭐5k)

• Cryptocoin

Playgrounds

• Script Playground

• Mnemonic Code generator

Read

• Mastering Bitcoin (⭐25k)

• Bitcoin Stackexchange

C++ Libraries

• libwally-core (⭐308)

Blockchain Explorers

• Blockexplorer.com

Playgrounds

• Script Debugger (⭐45)

Blockchain Explorers

• Smartbit

JavaScript Libraries

• Awesome CryptoCoinJS (⭐61)

PHP Libraries

• BlockTrail PHP SDK (⭐47)

Open Source Wallets

• Electrum

Blockchain Explorers

• Bitcoin Transaction Explorer (⭐184)

Java Libraries

• BitcoinJ

Open Source Wallets

• Coinb.in

JavaScript Libraries

• BlockTrail SDK NodeJS (⭐39)

Ruby Libraries

• Bitcoin-ruby (⭐922)

Python Libraries

• BlockTrail SDK Python (⭐23)

PHP Libraries

• PHP-OP_RETURN (⭐83)

Open Source Wallets

• CoPay by BitPay

Blockchain API and Web services

• Chain.com

Wallets API

• BIP32

JavaScript Libraries

• Bitcoinjs-lib (⭐6k)

Blockchain Explorers

• Chain.so

Blockchain API and Web services

• block.io

Wallets API

• Coinbase