I'm trying to understand how these wallet extensions sign transactions before sending them to the blockchain. With Solana CLI, you can simply reference a keypair.json and transactions go through without the need of the fancy UI. Same thing with Sugar CLI commands. I would like to know how to do that in javascript, I'm looking for something like transaction.signer = pubkey.

I've dug as far as this on metaplex candy machine ui repo's code, but I can't find how this wallet.signAllTransactions work technically. enter image description here

1 Answer 1


You can create a Keypair object from a private key:

import { Keypair } from '@solana/web3.js'
import base58 from 'bs58'

const yourPrivateKey = 'abcdef...' // base58 encoded
const keypair = Keypair.fromSecretKey(base58.decode(yourPrivateKey))

A Keypair is a Signer, so you can pass it to eg. transaction.sign(keypair). See docs here

Internally a wallet extension has access to the private key, so it can create a Keypair object and use it to sign transactions.

BTW you don't need to be writing a wallet extension to make use of this. Other use cases could be a Node script or an API that can perform a Solana transaction without any user input.

To do the same directly from a keypair file you can use this:

import { Keypair } from '@solana/web3.js'
import fs from 'fs'

const bytes = JSON.parse(fs.readFileSync('/path/to/keypair.json'))
const keypair = Keypair.fromSecretKey(new Uint8Array(bytes));

A keypair.json file contains a JSON array of the raw bytes, so you don't need to decode it.

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