Crypto Gloss

Spiral (Block)

Spiral (originally called Square Crypto) is the independent Bitcoin and Lightning Network open-source development team within Block, Inc. — the company formerly known as Square, led by Jack Dorsey. Founded in 2019, Spiral funds independent Bitcoin developers through grants and builds open-source infrastructure including the Lightning Development Kit (LDK) and Bitcoin Development Kit (BDK) — modular libraries enabling developers to integrate Bitcoin and Lightning payments into applications without running full infrastructure.

Background

Jack Dorsey announced the creation of Square Crypto in March 2019 with a simple mission: fund open-source Bitcoin development. The team operated independently from Block’s commercial products (Cash App, Square terminals). In December 2021, Square Crypto was renamed Spiral to reflect its expanded scope and standalone identity. Spiral sits alongside other Block Bitcoin initiatives including the Bitcoin hardware wallet project (Bitkey) and TBD (decentralized finance and Web5 research).

Key Products

Product Description
Lightning Development Kit (LDK) Rust-based modular library for integrating Lightning into any application without running a full LND/CLN node
Bitcoin Development Kit (BDK) Rust-based library for building Bitcoin wallets — descriptor-based, flexible chain backends
Developer Grants Direct financial support for open-source Bitcoin contributors
BTCPayServer Grants Spiral has been a major funder of BTCPayServer development

Significance of LDK and BDK

Before LDK and BDK, integrating Bitcoin or Lightning into applications required running and maintaining full node infrastructure (LND or Bitcoin Core). These libraries:

  • Allow developers to embed Bitcoin wallet and Lightning logic as libraries in mobile apps, exchanges, and services
  • Are backend-agnostic — they work with Electrum servers, Esplora, or custom backends
  • Are used in major products including Cash App’s Lightning integration and third-party wallets

Block Bitcoin Ecosystem

Spiral is one part of Block’s broader Bitcoin focus:

  • Cash App: Peer-to-peer Bitcoin buying, selling, and Lightning payments (consumer)
  • Spiral: Open-source developer tooling and grants
  • Bitkey: A hardware wallet product for self-custody
  • TBD: Web5 and decentralized identity research (Bitcoin-based)

Related Terms

Sources