> Aztec.nr API reference, v6.0.0 (mainnet and testnet). Index: https://docs.aztec.network/aztec-nr-api/v6.0.0/llms.txt

# Function check_nullifier_exists

Module: `noir_aztec::oracle::nullifiers`

```rust
pub unconstrained fn check_nullifier_exists(inner_nullifier: Field) -> bool
```

Returns `true` if the nullifier exists.

Note that a `true` value can be constrained by proving existence of the nullifier, but a `false` value should not be relied upon since other transactions may emit this nullifier before the current transaction is included in a block. While this might seem of little use at first, certain design patterns benefit from this abstraction (see e.g. `PrivateMutable`).