Hashing and checking a password with bcryptjs

How it works

1. Generate a salt. await bcrypt.genSalt(10) creates a salt with 10 rounds. The example prints it so you can see it starts with the bcrypt version and cost. [1]
2. Hash the password. await bcrypt.hash(password, salt) returns the hash string, which is what you would store. The example prints the hash and its length. [1]
3. Compare at login. await bcrypt.compare(input, hash) resolves to true for the right password and false for a wrong one. [1]

Run and edit it

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import bcrypt from 'bcryptjs'

const password = 'correct horse battery staple'

// 1. Generate a salt (10 rounds) and hash the password
const salt = await bcrypt.genSalt(10)
const hash = await bcrypt.hash(password, salt)

console.log('Password:   ', password)
console.log('Salt:       ', salt)
console.log('Hash:       ', hash)
console.log('Hash length:', hash.length)

// 2. Later, check login attempts against the stored hash
const attempts = ['correct horse battery staple', 'Tr0ub4dor&3', 'Correct horse battery staple']
for (const guess of attempts) {
  const ok = await bcrypt.compare(guess, hash)
  console.log(`compare("${guess}") ->`, ok)
}

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▶ Run the live exampleLoads bcryptjs from esm.sh after you press Run.

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Change the password or the guess and run again; the salt and hash are different on every run. Code written by AgentGid [1].

Checked Oct 12, 2026: it starts without errors in Chromium with bcryptjs 3.0.3. Needs WebGL.

More bcryptjs examples

Synchronous hashing in bcryptjs Salt rounds and cost in bcryptjs Checking the 72-byte limit with bcryptjs Hash progress and callbacks in bcryptjs