SwiftSync
SwiftSync is a proposed method for speeding up initial block download (IBD) using an untrusted hints file that indicates, for each output created during the sync, whether it is still unspent at the target block. Spent outputs are not stored in the UTXO set but are added to a hash aggregate from which each spent outpoint is later subtracted. An aggregate of zero at the end of the sync proves the hints were correct, allowing blocks to be validated in parallel with near-zero memory usage.
This topic description is a stub. We would welcome a pull request providing more background information about the topic.
Primary code and documentation
- SwiftSync - smarter synchronization with hints
- SwiftSync – Speeding up IBD with pre-generated hints (PoC)
Optech newsletter and website mentions
2026
- Proposal to use the SwiftSync hints file to speed up Utreexo IBD
- Bitcoin Core developer meeting transcript about SwiftSync
- Utreexod 0.5 introduces SwiftSync-based IBD
2025
- 2025 year-in-review: SwiftSync speedup for initial block download
- PR Review Club: decoupling Bitcoin Core validation from the UTXO set for SwiftSync-style nodes
-
Proposal and proof-of-concept implementation of SwiftSync showing a 5x IBD speedup
Previous Topic:
Swap-in Potentiam (SIP)
Next Topic:
Taproot