Hash progress and callbacks in bcryptjs

How it works

1. Callback style. bcrypt.genSalt(12, (err, salt) => …) and bcrypt.hash(password, salt, callback, progressCallback) pass their result to a callback instead of returning a promise. [1]
2. Track progress. The fourth argument receives a number from 0 to 1. The example prints it as a percentage with a small text bar. [1]
3. Work in chunks. Between progress calls the async API gives control back, so the page stays responsive. The last line checks the result with the callback form of bcrypt.compare. [1]

Run and edit it

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import bcrypt from 'bcryptjs'

const password = 'long-and-unique-passphrase'
const started = performance.now()
const bar = (p) => '#'.repeat(Math.round(p * 20)).padEnd(20, '.')

bcrypt.genSalt(12, (err, salt) => {
  if (err) return console.log('genSalt error:', err.message)
  console.log('Salt ready:', salt)

  bcrypt.hash(
    password,
    salt,
    (err, hash) => {
      if (err) return console.log('hash error:', err.message)
      console.log('Done in', (performance.now() - started).toFixed(0), 'ms')
      console.log('Hash:', hash)
      bcrypt.compare(password, hash, (err, res) => console.log('compare ->', res))
    },
    (p) => console.log(`progress [${bar(p)}] ${(p * 100).toFixed(0)}%`)
  )
})

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Raise the round count to 13 and you will see more progress lines before the hash prints. 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

Hashing and checking a password with bcryptjs Synchronous hashing in bcryptjs Salt rounds and cost in bcryptjs Checking the 72-byte limit with bcryptjs