How to Restore a Keypair from a Mnemonic

Many wallet extensions use mnemonics to represent their secret keys. You can convert the mnemonic to Keypairs for local testing.

Restoring BIP39 format mnemonics

import { Keypair } from "@solana/web3.js";
import * as bip39 from "bip39";

const mnemonic =
  "pill tomorrow foster begin walnut borrow virtual kick shift mutual shoe scatter";

// arguments: (mnemonic, password)
const seed = bip39.mnemonicToSeedSync(mnemonic, "");
const keypair = Keypair.fromSeed(seed.slice(0, 32));

console.log(`${keypair.publicKey.toBase58()}`);

// output: 5ZWj7a1f8tWkjBESHKgrLmXshuXxqeY9SYcfbshpAqPG

Restoring BIP44 formant mnemonics

import { Keypair } from "@solana/web3.js";
import { HDKey } from "micro-ed25519-hdkey";
import * as bip39 from "bip39";

const mnemonic =
  "neither lonely flavor argue grass remind eye tag avocado spot unusual intact";

// arguments: (mnemonic, password)
const seed = bip39.mnemonicToSeedSync(mnemonic, "");
const hd = HDKey.fromMasterSeed(seed.toString("hex"));

for (let i = 0; i < 10; i++) {
  const path = `m/44'/501'/${i}'/0'`;
  const keypair = Keypair.fromSeed(hd.derive(path).privateKey);
  console.log(`${path} => ${keypair.publicKey.toBase58()}`);
}