Synchronous hashing in bcryptjs

How it works

1. Salt, then hash. bcrypt.genSaltSync(10) returns a salt string, and bcrypt.hashSync(password, salt) returns the hash right away. [1]
2. Auto-generate the salt. Passing a number instead of a salt, as in bcrypt.hashSync(password, 10), creates the salt for you. Hashing the same password twice gives two different hashes because each gets its own salt. [1]
3. Verify with compareSync. bcrypt.compareSync(password, hash) returns a boolean. Both hashes validate the same password. [1]

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import bcrypt from 'bcryptjs'

const password = 'hunter2'

// Explicit salt
const salt = bcrypt.genSaltSync(10)
const hashA = bcrypt.hashSync(password, salt)

// Salt generated from a round count
const hashB = bcrypt.hashSync(password, 10)

console.log('Salt:   ', salt)
console.log('Hash A: ', hashA)
console.log('Hash B: ', hashB)
console.log('Same hash twice?', hashA === hashB)

console.log('compareSync(password, hashA):', bcrypt.compareSync(password, hashA))
console.log('compareSync(password, hashB):', bcrypt.compareSync(password, hashB))
console.log('compareSync("hunter3", hashA):', bcrypt.compareSync('hunter3', hashA))

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Run it twice: the two hashes differ every time, but both compareSync checks print true. Code written by AgentGid [1].

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

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