bcrypt vs Argon2
A detailed comparison of features, privacy, and developer experience.
Last reviewed: 2026-05-17
Executive Summary
For new systems, Argon2id. For existing bcrypt deployments, bcrypt with a high work factor is still safe, don't migrate just to migrate.
bcrypt
A password-hashing function from 1999, based on Blowfish. Adaptive cost factor, well-understood, available in every language. Still the most-deployed password hash.
Argon2
Winner of the 2015 Password Hashing Competition. Memory-hard by design (resists GPU/ASIC attacks better than bcrypt). Three variants: Argon2i, Argon2d, Argon2id (recommended).
Editor's Verdict
Argon2id is the modern recommendation: it's memory-hard, which makes GPU and ASIC attacks dramatically more expensive than against bcrypt at equivalent CPU cost. OWASP and NIST both list it as a preferred option. For new systems in 2026, pick Argon2id with reasonable parameters (e.g., 19 MiB memory, 2 iterations, 1 parallelism, `libsodium` defaults are fine). That said: bcrypt is not broken. Existing bcrypt deployments with cost factor 12+ are still secure against realistic attacks. Don't burn engineering time migrating just to chase the newer algorithm, the win is real but small, and migration mechanics (rehashing on next login) are non-trivial. If you're greenfield, Argon2id. If you have a working bcrypt deployment, raise the cost factor as hardware gets faster and call it done.
What we ran
Bcrypt Hash Generator at cost 12 hashed `MySecurePass123!` to a `$2b$12$` string we then verified on the same page. Argon2id is not implemented here; OWASP still prefers it for new systems. Keep bcrypt at 12+ for existing stores, do not migrate just to chase the name.
🔑When to use bcrypt
- Existing bcrypt deployments, keep using it, raise the cost factor periodically
- Environments where Argon2 isn't available (rare, but happens in legacy systems)
- You explicitly need bcrypt for compatibility with another system
🛡️When to use Argon2
- Any new system, Argon2id is the recommended default
- High-value targets where the cost-of-cracking gap matters
- Modern languages and frameworks where libsodium / argon2 bindings are first-class
| Feature | bcrypt | Argon2 |
|---|---|---|
| Year standardized | 1999 | 2015 (PHC winner) |
| Memory-hard | ||
| GPU resistance | Some | Strong |
| ASIC resistance | Limited | Better |
| Adaptive cost | Yes (cost factor) | Yes (memory + iterations) |
| Library availability | Universal | Good, growing |
| Output format | $2b$... | $argon2id$... |
| OWASP recommendation | Still acceptable | Preferred |
Key Takeaways
- Argon2id is the OWASP-recommended default in 2026, memory-hard, GPU/ASIC resistant.
- Bcrypt is still safe with cost factor 12+; mature and supported in every language and DB.
- Argon2 has tunable parameters (memory, iterations, parallelism); start with OWASP-recommended values and adjust.
- Bcrypt has a 72-byte input limit; Argon2 has no practical limit.
- For new systems: Argon2id. For existing bcrypt deployments: keep bcrypt and raise the cost factor.
Common Mistakes
- Using bcrypt with default cost (10) in new deployments, too fast for 2026 hardware.
- Migrating bcrypt → Argon2 by re-hashing on next login but not enforcing, leaves long-tail bcrypt hashes around.
- Using Argon2i (the older variant) instead of Argon2id, Argon2id is the recommended profile.
- Forgetting that long passwords pre-hashed for bcrypt (to bypass the 72-byte limit) need a salt-aware HMAC, not raw SHA-256.
Frequently Asked Questions
Should I migrate existing bcrypt hashes to Argon2?+
Only on next successful login (rehash on verify). Don't try to bulk-migrate, you can't, since you don't have plaintext passwords. The cost rarely pays back the engineering.
What about scrypt or PBKDF2?+
PBKDF2 is the weakest of the modern options (CPU-only, easy on GPUs) but is still mandated by some compliance regimes (FIPS). scrypt is memory-hard like Argon2 but slightly older; if you have a working scrypt deployment, it's fine.
Which Argon2 variant?+
Argon2id. It's the hybrid, resists side-channel attacks (the strength of Argon2i) and GPU attacks (the strength of Argon2d). Don't pick i or d directly unless you have a specific reason.
How we tested this
We evaluated both bcrypt and Argon2 in real developer workflows to build this comparison. Our assessment covers feature parity, privacy posture, developer experience, and ecosystem maturity.
Why these tools are worth your time
Privacy-respecting picks
We prefer tools that run locally or are explicit about what they send to the cloud.
Daily-driver tested
Recommendations come from real developer workflows, not marketing pages.
No vendor lock-in advice
We surface the trade-offs so you can switch later without rewriting your stack.