Transaction extra

Tagged data alongside the transaction

The format defines identifiers for supported extra fields. A parser uses those tags to distinguish a transaction public key from other supported data rather than interpreting the entire field as free-form text.

Wallets rely on transaction public keys during output scanning. Some transactions also need additional public keys. These keys support recipient detection without writing the recipient's ordinary address into each output.

References: Monero transaction extra definitions · Monero source: wallet/wallet2.cpp

Visibility depends on the field

Placement in extra does not imply encryption. A supported encrypted short payment ID has its own construction, while transaction public keys are public by design. Inspect the specific field rather than assigning one privacy property to the entire container.

Custom data can make a transaction easier to distinguish from ordinary wallet traffic. Do not place names, account credentials or private wallet material in transaction metadata. A public blockchain is not a suitable destination for secrets.

References: Monero transaction extra definitions · Monero source: wallet/wallet2.cpp

Example

A wallet scans the transaction extra field for the public key information needed to recognize its outputs. Finding that key does not expose the recipient public wallet address.

References: Monero transaction extra definitions · Monero source: wallet/wallet2.cpp

Limits and cautions

Extra is not a private notes field. Data placed there is part of the public transaction. Wallet notes kept only on a device are different, and arbitrary extra data can create a distinctive public marker.

References: Monero transaction extra definitions