Blockstream Green uses the BIP39 standard—the most widely-adopted format in the Bitcoin industry—to generate your recovery phrase.
Recovery phrases generated using the BIP39 standard consist of either 12 or 24 words from a library of 2048 pre-specified terms. Blockstream Green recovery phrases are 12 words by default.
As a hierarchical deterministic wallet, Blockstream Green uses the BIP32 standard to derive the child keys for its wallet.
Although Blockstream Green uses industry standards for recovery phrase generation, wallets created in Blockstream Green using Multisig Shield cannot be restored on other wallet software. This is due to the unique multisig security model used for Multisig Shield wallets. In comparison, wallets that use Singlesig can be restored on most other wallet software (e.g. Electrum).
In order to restore BIP39 wallets created on other wallet software, you can select Migrate Another Wallet when restoring a wallet on Blockstream Green.
Note: If you enter your recovery phrase from a Multisig Shield wallet into a different wallet app that supports BIP39, the recovery phrase may be accepted by the app, but it will generate an empty single-signature wallet. Any transactions sent from or received to this wallet will be completely separate from your Blockstream Green wallet.