Global Variables

Similar to Solidity's global block variable, Aztec exposes contextual values within each function via the context object.

Aztec has two execution environments—Private and Public—each with different available globals.

Private Global Variables

Private functions access transaction context via TxContext:

tx-context

#[derive(Deserialize, Eq, Serialize)]
pub struct TxContext {
    // The chain ID on which this transaction is executed.
    pub chain_id: Field,
    // The version of the L1 Rollup contract.
    pub version: Field,
    // The gas settings for the transaction.
    pub gas_settings: GasSettings,
}

^{_{Source code: noir-projects/noir-protocol-circuits/crates/types/src/abis/transaction/tx_context.nr#L8-L18}}

The following fields are accessible via context methods:

Chain Id

The unique identifier for the Aztec network instance (not the Ethereum chain the rollup settles to).

context.chain_id();

Version

The Aztec protocol version number. The genesis block has version 1.

context.version();

Gas Settings

The gas limits, max fees per gas, and inclusion fee set by the user for the transaction.

context.gas_settings();

Public Global Variables

Public functions access block-level context via GlobalVariables:

global-variables

#[derive(Deserialize, Eq, Serialize)]
pub struct GlobalVariables {
    pub chain_id: Field,
    pub version: Field,
    pub block_number: u32,
    pub slot_number: Field,
    pub timestamp: u64,
    pub coinbase: EthAddress,
    pub fee_recipient: AztecAddress,
    pub gas_fees: GasFees,
}

^{_{Source code: noir-projects/noir-protocol-circuits/crates/types/src/abis/global_variables.nr#L7-L19}}

note

Not all fields in GlobalVariables are exposed via context methods. The coinbase, fee_recipient, and slot_number fields are used internally by the protocol.

Public functions have access to chain_id() and version() (same syntax as private), plus the following block-level values:

Timestamp

The unix timestamp when the block is executed. Provided by the block proposer, so it may have slight variance. Always increases monotonically.

context.timestamp();

Block Number

The sequential block identifier. Genesis block is 1, incrementing by 1 for each subsequent block.

context.block_number();

Gas Fees

The current L2 and DA gas prices for the block. You can access gas-related information via:

context.l2_gas_left();       // Remaining L2 gas
context.da_gas_left();       // Remaining DA gas
context.base_fee_per_l2_gas(); // L2 gas price
context.base_fee_per_da_gas(); // DA gas price
context.transaction_fee();   // Final tx fee (only available in teardown phase)

Why do available globals differ between environments?

Private functions execute on the user's device before the transaction is submitted, so they cannot know which block will include the transaction. Therefore, timestamp and block_number are unavailable in private context.

Public functions execute on a sequencer who knows the current block's timestamp and number, making these values accessible.