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Specialization Areas

Bitcoin Core is a large project. Most contributors eventually specialize in one or two subsystems. This section provides an overview of the main areas you can focus on.

P2P Networking​

The peer-to-peer layer handles all communication between nodes.

What you'd work on:

  • Connection management and peer selection
  • Message relay policies (transaction, block, address)
  • Eclipse attack mitigations
  • Network privacy (BIP-324 encrypted transport)
  • Tor, I2P, and CNET support

Key files: src/net.cpp, src/net_processing.cpp, src/addrman.cpp

Current topics:

  • Erlay (BIP-330) — Bandwidth-efficient transaction relay
  • Package relay — Relay related transactions as packages
  • Encrypted P2P (BIP-324) — Opportunistic encryption

Mempool Policy​

The mempool manages unconfirmed transactions and decides which to relay and mine.

What you'd work on:

  • Fee estimation algorithms
  • Transaction relay policy (standardness rules)
  • Replace-By-Fee (RBF) logic
  • Package acceptance and CPFP (Child-Pays-For-Parent)
  • Mempool eviction policies

Key files: src/txmempool.cpp, src/policy/, src/validation.cpp

Current topics:

  • Package relay and package RBF
  • Cluster mempool — Restructuring for better fee-based ordering
  • Ephemeral anchors — Zero-fee anchor outputs for Lightning

Wallet​

The wallet subsystem manages keys, constructs transactions, and tracks balances.

What you'd work on:

  • Descriptor wallets (modern key management)
  • Coin selection algorithms
  • Transaction construction and signing
  • PSBT (Partially Signed Bitcoin Transactions)
  • Hardware wallet integration (HWI)

Key files: src/wallet/

Current topics:

  • Miniscript integration — Composable spending policies
  • Silent Payments (BIP-352) — Reusable stealth addresses
  • Coin selection improvements

Mining Interface​

The mining subsystem constructs block templates and interfaces with mining software.

What you'd work on:

  • Block template construction (getblocktemplate)
  • Transaction selection for blocks
  • Stratum V2 integration
  • Mining pool interfaces

Key files: src/node/miner.cpp, src/rpc/mining.cpp

Script & Consensus​

The script interpreter and consensus engine are the most critical parts of Bitcoin.

What you'd work on:

  • Script opcode implementation
  • Signature verification (ECDSA, Schnorr)
  • Taproot/Tapscript execution
  • Potential future opcodes (OP_CTV, OP_CAT)

Key files: src/script/, src/consensus/

Current topics:

  • OP_CHECKTEMPLATEVERIFY (BIP-119) — Covenant primitive
  • OP_CAT — Concatenation opcode re-enablement
  • Great Script Restoration — Re-enabling disabled opcodes

How to Choose​

If you enjoy...Consider...
Networking and distributed systemsP2P Networking
Algorithm design and optimizationMempool Policy
User-facing features and UXWallet
Performance and low-level optimizationMining Interface
Cryptography and formal reasoningScript & Consensus

Most contributors start by reviewing PRs in their area of interest before writing their own code. Review is the best way to learn a subsystem deeply.