Finishing what Section 8 started.
The Bitcoin whitepaper described Simplified Payment Verification (SPV) in 2008. Seventeen years later, true lightweight verification infrastructure remains incomplete. Most light wallets trust servers rather than verify proofs themselves.
bitcoin.cc provides foundational infrastructure for Compact Clients: block headers, merkle proofs, and tools for lightweight Bitcoin verification.
Compact Clients use cryptographic proofs to verify Bitcoin without requiring full blockchain data. The "compactness" refers to proof size, not capability.
Three levels of compact verification:
bitcoin.cc provides infrastructure for all levels, starting with headers.
"It is possible to verify payments without running a full network node. A user only needs to keep a copy of the block headers of the longest proof-of-work chain, which he can get by querying network nodes until he's convinced he has the longest chain, and obtain the Merkle branch linking the transaction to the block it's timestamped in." — Satoshi Nakamoto, Bitcoin: A Peer-to-Peer Electronic Cash System, Section 8
A block header is only 80 bytes — containing the proof-of-work, previous block hash, merkle root, timestamp, and difficulty target. The entire Bitcoin header chain is under 100MB.
With headers alone, you can:
Headers are grouped into epochs of 2016 blocks — the Bitcoin difficulty adjustment period. Each epoch represents approximately two weeks of blocks.
All endpoints return JSON. No authentication required.
GET /headers/latest.json
Chain tip and epoch summary
GET /headers/current.json
Current incomplete epoch (updates)
GET /headers/epoch/{n}.json
Archived epoch (2016 headers, immutable)
GET /headers/epoch/0.json
Genesis epoch (blocks 0–2015)
All header data and code is open source and available on GitHub. Verify independently. Trust, but verify.