> For the complete documentation index, see [llms.txt](/llms.txt).

# Secp256k1 Private Key

The `getPrivateKey` method returns the user's secp256k1 private key (the elliptic curve used by Ethereum and EVM-compatible chains). Use this key to sign transactions on EVM-compatible chains.

When you set `useSFAKey` to `true` in `Web3AuthOptions`, this method returns the single-factor authentication (SFA) key instead of the standard private key.

## Usage[​](#usage "Direct link to Usage")

```
let privateKey = web3Auth.getPrivateKey()

```