bcryptjs
Pure JavaScript implementation of bcrypt password hashing with no native dependencies. Bcryptjs provides password hashing and comparison for user authentication. Uses the bcrypt algorithm with configurable work factor (cost) for adaptive security. Works in both Node.js and browsers unlike the native bcrypt package.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Pure JS bcrypt implementation is auditable and has no native code vulnerabilities. Cost factor must be calibrated to hardware. 72-byte truncation is a known limitation requiring pre-hashing for long passwords.
⚡ Reliability
Best When
You need dependency-free password hashing in Node.js without native module compilation, or in environments with build constraints.
Avoid When
You want the gold standard (Argon2) or need maximum performance — use argon2 npm package or bcrypt (native) for production at scale.
Use Cases
- • Hash user passwords before storage in database with configurable cost factor for security vs performance balance
- • Verify submitted passwords against stored hashes for user login authentication
- • Use async bcrypt operations to avoid blocking Node.js event loop during expensive hash operations
- • Build authentication systems without native compilation dependencies (unlike bcrypt npm package)
- • Hash passwords in environments where native modules are unavailable (AWS Lambda, restricted builds)
Not For
- • Hashing non-password data — bcrypt is designed for passwords; use SHA-256 or BLAKE3 for general hashing
- • High-throughput password hashing — bcrypt is intentionally slow; for bulk operations consider Argon2 with dedicated workers
- • Encryption — bcrypt is a one-way hash, not reversible encryption; use AES-GCM for encryption needs
Interface
Authentication
Library with no auth requirement.
Pricing
Free and open source.
Agent Metadata
Known Gotchas
- ⚠ Always use async bcrypt.hash() and bcrypt.compare() — sync versions (hashSync, compareSync) block the event loop for 100-500ms at cost=10, killing server throughput
- ⚠ Cost factor (saltRounds) of 10 is the recommended minimum — lower values are faster but less secure; 12 is a good 2024 default balancing security and speed
- ⚠ bcrypt.compare() returns false for mismatches, it does NOT throw — agents checking auth must check the boolean return, not catch errors
- ⚠ Bcrypt truncates passwords at 72 bytes — passwords longer than 72 characters are silently truncated; pre-hashing with SHA-256 is needed for long password support
- ⚠ bcryptjs is ~30% slower than the native bcrypt package — for high-traffic auth endpoints, consider the native package if build environment supports it
- ⚠ The hash output includes the salt — store only the hash string; do NOT store salt separately as it's embedded in the hash output format
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for bcryptjs.
Scores are editorial opinions as of 2026-03-06.