extensions.mdx

title	Extensions
description	Learn how to enable token extensions to add optional features to token mints and accounts using the Token Extensions Program (Token 2022) in an Anchor program.

What are Token Extensions?

The Token Extensions Program (Token 2022) provides additional features through additional instructions referred to as extensions. Extensions are optional functionality that can be added to a token mint or token account. You can find the implementation of these extension instructions in the Token Extensions Program source code.

Each extension adds specific state that is usually initialized during mint or token account creation. When initializing either type of account, you can enable multiple extensions simultaneously to add different functionality. However, most extensions cannot be added after an account is created - you must include all desired extensions during the initial account creation. This is an important consideration when designing your token, as you'll need to plan ahead for which features you want your token to support. The exceptions to this, which require the account to be initialized before they are added, are:

• cpi-guard
• memo-transfer
• token-group
• token-member
• token-metadata

Some extensions are incompatible with each other and cannot be enabled simultaneously on the same token mint or token account. For example, you cannot combine the NonTransferable extension with the TransferFeeConfig extension, since they have conflicting behaviors.

The Token Extensions Program defines an ExtensionType enum that specifies all available extensions that can be added to a token mint or token account. Each variant represents a different extension with unique functionality.

The ExtensionType enum is defined as follows:

/// Extensions that can be applied to mints or accounts.  Mint extensions must
/// only be applied to mint accounts, and account extensions must only be
/// applied to token holding accounts.
#[repr(u16)]
#[cfg_attr(feature = "serde-traits", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "serde-traits", serde(rename_all = "camelCase"))]
#[derive(Clone, Copy, Debug, PartialEq, TryFromPrimitive, IntoPrimitive)]
pub enum ExtensionType {
    /// Used as padding if the account size would otherwise be 355, same as a
    /// multisig
    Uninitialized,
    /// Includes transfer fee rate info and accompanying authorities to withdraw
    /// and set the fee
    TransferFeeConfig,
    /// Includes withheld transfer fees
    TransferFeeAmount,
    /// Includes an optional mint close authority
    MintCloseAuthority,
    /// Auditor configuration for confidential transfers
    ConfidentialTransferMint,
    /// State for confidential transfers
    ConfidentialTransferAccount,
    /// Specifies the default Account::state for new Accounts
    DefaultAccountState,
    /// Indicates that the Account owner authority cannot be changed
    ImmutableOwner,
    /// Require inbound transfers to have memo
    MemoTransfer,
    /// Indicates that the tokens from this mint can't be transferred
    NonTransferable,
    /// Tokens accrue interest over time,
    InterestBearingConfig,
    /// Locks privileged token operations from happening via CPI
    CpiGuard,
    /// Includes an optional permanent delegate
    PermanentDelegate,
    /// Indicates that the tokens in this account belong to a non-transferable
    /// mint
    NonTransferableAccount,
    /// Mint requires a CPI to a program implementing the "transfer hook"
    /// interface
    TransferHook,
    /// Indicates that the tokens in this account belong to a mint with a
    /// transfer hook
    TransferHookAccount,
    /// Includes encrypted withheld fees and the encryption public that they are
    /// encrypted under
    ConfidentialTransferFeeConfig,
    /// Includes confidential withheld transfer fees
    ConfidentialTransferFeeAmount,
    /// Mint contains a pointer to another account (or the same account) that
    /// holds metadata
    MetadataPointer,
    /// Mint contains token-metadata
    TokenMetadata,
    /// Mint contains a pointer to another account (or the same account) that
    /// holds group configurations
    GroupPointer,
    /// Mint contains token group configurations
    TokenGroup,
    /// Mint contains a pointer to another account (or the same account) that
    /// holds group member configurations
    GroupMemberPointer,
    /// Mint contains token group member configurations
    TokenGroupMember,
    /// Mint allowing the minting and burning of confidential tokens
    ConfidentialMintBurn,
    /// Tokens whose UI amount is scaled by a given amount
    ScaledUiAmount,
    /// Tokens where minting / burning / transferring can be paused
    Pausable,
    /// Indicates that the account belongs to a pausable mint
    PausableAccount,

    /// Test variable-length mint extension
    #[cfg(test)]
    VariableLenMintTest = u16::MAX - 2,
    /// Padding extension used to make an account exactly Multisig::LEN, used
    /// for testing
    #[cfg(test)]
    AccountPaddingTest,
    /// Padding extension used to make a mint exactly Multisig::LEN, used for
    /// testing
    #[cfg(test)]
    MintPaddingTest,
}

Each extension adds specialized functionality by including additional state that must be initialized when creating a mint or token account. All extension specific state is stored in the in the tlv_data field, which follows the base account data type. The tlv_data (containing extension state) must be further deserialized according to the specific extension types enabled for that account.

/// Encapsulates immutable base state data (mint or account) with possible
/// extensions, where the base state is Pod for zero-copy serde.
#[derive(Debug, PartialEq)]
pub struct PodStateWithExtensions<'data, S: BaseState + Pod> {
    /// Unpacked base data
    pub base: &'data S,
    /// Slice of data containing all TLV data, deserialized on demand
    // [!code word:tlv_data]
    // [!code highlight]
    tlv_data: &'data [u8],
}

Examples

The anchor-spl crate provides a token_2022_extensions module that contains helper functions and types for working with token extension instructions.

You can find examples for how to work with Token Extensions in an Anchor program in this program examples repository.

Note that while the anchor-spl crate provides helper functions for working with Token Extensions, not all extension instructions have been fully implemented yet. You may need to manually implement CPI calls for some extension instructions.