Taproot

Taproot is a Bitcoin protocol upgrade that introduced Schnorr signatures and a more private, efficient way to commit to multiple spending conditions. It activated in November 2021 through a backward-compatible soft fork. Taproot outputs can be spent through a key path or by revealing a selected script path.

The upgrade combines BIP340, BIP341, and BIP342. BIP340 defines Schnorr signatures for the secp256k1 curve. BIP341 defines Taproot output and spending rules, including a tree of possible scripts. BIP342 updates Bitcoin Script for Taproot through Tapscript. Together, they provide a foundation for flexible policies and future extensions.

A key-path spend looks like a straightforward signature even when several participants cooperatively control the funds using an appropriate signing protocol. If cooperation fails, a participant can reveal the relevant script branch and satisfy its conditions. Other unused branches remain hidden. This can save block space and disclose less about the wallet's complete policy than older constructions.

Taproot matters for multisignature wallets, payment channels, and more advanced Bitcoin contracts. Schnorr signatures support useful aggregation properties, although secure multi-party signing requires protocols beyond simply adding signatures together. Smaller or less revealing transactions can reduce fees in some cases. Savings depend on the policy and spending path, so Taproot is not always cheaper than every SegWit alternative.

Taproot addresses on Bitcoin mainnet generally begin with bc1p and use the Bech32m checksum. Existing coins do not need conversion, and older address types remain valid. Wallet and service support varies for receiving, spending, recovery, hardware display, and policy creation. Users should test new workflows and verify that backups restore the intended Taproot accounts.

Privacy improvements have limits. Amounts and transaction graphs remain public, and distinctive behavior can reveal wallet relationships. Users should verify addresses on a trusted screen and understand any script recovery path before depositing. Taproot expanded Bitcoin's signature and scripting capabilities without creating a new asset, but safe benefits depend on correct wallet implementation, key management, and compatible service support.

Developers need test vectors and reviewed libraries for Bech32m encoding, tagged hashes, signature rules, and script-tree construction. Losing one branch, internal key, or participant's recovery information can make an intended spending path unusable. Wallet backups should preserve more than a seed when custom scripts or multisignature policies require descriptors, participant keys, and threshold details for complete recovery.